President Obama called on Russian President Vladimir Putin to agree to a diplomatic solution to the escalating Ukrainian conflict Tuesday, telling Putin in a phone call that “the costs for Russia will rise” if its aggression continues.

In a separate phone call with Ukrainian President Petro Poroshenko, Obama also pledged continuing financial assistance to the eastern European country, the White House said.

The round of telephone diplomacy comes the day before a round of talks continues in Minsk, Belarus — a follow-up to an agreement reached there last September. NATO counties, led by the Germany, France and the United States, are pressuring Russia to withdraw troops and armaments from separatist-controlled territories in eastern Ukraine.

The serious escalation of fighting in Ukraine is pushing President Barack Obama closer to the proxy war with Russia that he has long sought to avoid

In effect, Washington would be sending weapons to be used against Russian forces at a time when the Kremlin is increasingly hostile to the West and has shown it is ready to escalate a showdown.

There is no guarantee that funneling sophisticated U.S. armaments into the conflict could be decisive, and the gambit could antagonize Vladimir Putin, Russia’s increasingly isolated and hard-to-read leader. In a sign of possible administration push back against Carter’s remarks, the top NATO general Philip Breedlove told the Associated Press in an interview on Thursday that arming Ukraine could spark a “more strident” reaction from Russia.

U.S. provision of military aid to Ukraine would be seen by Moscow as a declaration of war and spark a global escalation of Ukraine’s separatist conflict, Russian defense analysts said…

But if such aid were sent, “Russia would reasonably consider the U.S. to be a direct participant in the conflict,” said Evgeny Buzhinsky, a military expert at the Moscow-based PIR Center.

Speaking to The Moscow Times on a condition of anonymity, a member of the Russian Defense Ministry’s public advisory board warned that Moscow would not only up the ante in eastern Ukraine, “but also respond asymmetrically against Washington or its allies on other fronts.”

Defense Secretary nominee Ash Carter on Wednesday said he would be “inclined” to provide weapons to the Ukraine, in contrast with the White House’s current policy.

“I am inclined in the direction of providing them arms,” he told members of the Senate Armed Services Committee at his confirmation hearing.

“The nature of those arms, I can’t say right now,” he said, noting that he would have to confer with military officials…

But White House press secretary Josh Earnest said it was “unrealistic” to think the United States could equip Ukraine to match Russia’s military power, and that the administration believed the crisis was best resolved “around the negotiating table.”

The White House came under bipartisan pressure from both sides of the Capitol to provide weapons to Ukraine Thursday.

Republicans and Democrats on the Senate Armed Services Committee made a big push on the issue, while a bipartisan group of House members called for the same course of action in a letter…

“We are calling on the Administration to increase its support for Ukraine. Tighter sanctions and greater humanitarian assistance should be part of that support, but now, more than ever, the U.S. must supply Ukraine with the means to defend itself,” they said in their letter. 

Rep. Adam Schiff (D-Calif.), ranking member on the House Intelligence committee, was the lead signatory on the letter. He was joined by more than 30 Republicans and Democrats.

Germany’s rejection of supplying weapons to Ukrainian forces fighting pro-Russian rebels may heighten the domestic pressure on a reluctant U.S. President Barack Obama to deliver the arms…

Obama won’t authorize weapons deployment if Merkel signals that she won’t publicly condemn individual nations from arming Ukraine, the three people said. If she opposes any unilateral supplying of weapons, Obama will explain his decision to follow her lead by citing the importance of keeping a united front against Putin and the risk of triggering a proxy war with Russia, the people said…

[Critics within the administration] argue that it’s important to push back hard against Putin in Ukraine and elsewhere to prevent the conflict from escalating out of control, the official said. The debate over arming Ukraine masks a much deeper analytical split about relations with Russia within the administration and NATO, he added.

The shift in the White House’s openness about lethal aid accompanies the prospect of more violence. On Monday, as The Wall Street Journal reported, the leader of the Russian-backed rebel separatists announced plans “to raise up to 100,000 troops to fight in eastern Ukraine.” The report added: “The announcement comes as Kiev is enlarging its own army through a new round of conscriptions.” (On Tuesday, separatists reportedly downed another Ukrainian jet.)

A few things have kept the White House from sending arms to Ukraine⎯the crippling sanctions already in place against Russia, the White House’s semi-aversion to foreign entanglements, and, most saliently, the question of whether American arms will inflame the situation. “Russia is not ready to back down and it can match the U.S.,” one expert told Bloomberg.

The New York Times noted that the president’s thinking may have been swayed by a report submitted by eight former high-ranking officials. The authors proposed sending $3 billion in weapons and equipment to provide Ukraine with enough retaliatory power that, in the report’s words, “Moscow will deterred from further aggression.”

[Polish Defense Minister Tomasz] Siemoniak also voiced concern that any military support for Ukraine by Nato states must take note of a potential escalation of the conflict by Moscow.

“Russia is a power that has a nuclear arsenal and western politicians have to keep this in mind, would it not lead to a global war?” he said in Warsaw.

Polish officials fear that military support would also require western countries to send military personnel to operate equipment or train Ukrainian forces, which could lead to a further escalation in the conflict, rather than suppressing it.

U.S. aid is a propaganda gift to the Kremlin, allowing it to bring its covert war out of the shadows. Putin controls the country’s key media, and Russians would support any fight against U.S. hegemony, whatever the economic and human cost…

Faced with Russian escalation, the United States would either have to back down and lose credibility or — more likely — commit to funding a proxy war on the European continent.

This would cost thousands more lives, create a continental security crisis, rupture Russia-EU ties and damage Europe’s economy further through sanctions and tightening of borders.

This is all about NATO expansion which scares the daylights out of the Russians. It shouldn’t, but it does, and it’s not hard to understand why. Just ask yourself how the British would feel if the USSR won the Cold War and the Warsaw Pact expanded to Paris and Brussels. London would feel like it’s “next.” London would have cause to feel like it’s “next.” That’s exactly how it looked from Moscow’s point of view when former vassals like Lithuania and Estonia joined up with Germany and France—and the United States…

“I believe the Russians are mobilizing right now for a war that they think is going to happen in five or six years,” said US Army Commander in Europe Lt. Gen. Frederick “Ben” Hodges. “Not that they’re going to start a war in five or six years, but I think they are anticipating that things are going to happen, and that they will be in a war of some sort, of some scale, with somebody within the next five or six years.”

The solution from Russia’s point of view—as always—is to either control or destabilize as many “buffer” states as it can. Any of its smaller neighbors that get a little too uppity will find themselves undermined from within or outright invaded, and in the modern era they’re likely to find scraps of territory “annexed” by Moscow to indefinitely prevent them from joining NATO. No one in NATO wants to admit a nation as a new member state that has a disputed territory conflict with Russia. It’s dangerous. That’s ultimately what Russia’s invasion of Georgia in 2008 was about, and it’s the main reason Russia annexed Ukraine’s Crimea peninsula last year.

Putin has already achieved his primary objective and doesn’t need to do much else at this point except not lose the rest of the war. If the United States gets even indirectly involved, he’ll just ramp it up. He needs to win in Ukraine far more than we do, and unlike us he’s more than willing to deploy his own forces directly.

Proponents of arming Ukraine have a second line of argument. The key to success, they maintain, is not to defeat Russia militarily, but to raise the costs of fighting to the point where Mr. Putin will cave. The pain will supposedly compel Moscow to withdraw its troops from Ukraine and allow it to join the European Union and NATO and become an ally of the West.

This coercive strategy is also unlikely to work, no matter how much punishment the West inflicts. What advocates of arming Ukraine fail to understand is that Russian leaders believe their country’s core strategic interests are at stake in Ukraine; they are unlikely to give ground, even if it means absorbing huge costs.

Great powers react harshly when distant rivals project military power into their neighborhood, much less attempt to make a country on their border an ally. This is why the United States has the Monroe Doctrine, and today no American leader would ever tolerate Canada or Mexico joining a military alliance headed by another great power.

Russia is no exception in this regard.

Further, even if the president went along with the McCain plan, and the United States did supply military aid to Kiev, are we so sure that their troops are equipped with the proper training to use these weapons? Doubtful. And if the United States then has to send in military advisers to train the Ukrainian troops, what happens if one of them gets killed by Russian forces? Is McCain willing to risk a shooting war—or possibly a nuclear war—with Russia over the fate of the Donbas? It would seem so.

Another objection to arming Kiev is the nature of the regime to which we are propping up. The government in Ukraine is still wondrously corrupt. It is led by an oligarch who many conveniently forget was closely tied to ancien regime, having served as minister of trade in 2012 and as minister of foreign affairs in 2009-2010.

Its armed forces are an admixture of volunteer battalions and regular forces that are not under a unified command. What is more, Kiev is struggling with recruitment efforts. According to the Ukrainian daily Korrespondent, only 6 percent of those showing up this year for the call to military service have done so voluntarily. Does McCain propose to send arms to an army that has no recruits with which to use them? Are we so sure that the weapons McCain would like to provide Kiev wouldn’t end up in the wrong hands, as they have so many times before, in Iraq, in Syria, in Libya and in Afghanistan?

This Russian invasion requires American honesty. Today, in the Baltic States, Russia is threatening pro-Western politicians and kidnapping intelligence officers. And in Ukraine, Russia is stealing a nation. In recent weeks, Russia has escalated offensive actions across eastern Ukraine. Arming, mobilizing, and directing Ukrainian separatists against the Kiev government, President Putin has shredded last September’s Minsk agreement. Under this deal, Russia had agreed to cease its support for rebel aggression. Instead, it has done the exact opposite. This was predictable. As I wrote in December, lower oil prices and Putin’s philosophy meant that Russia’s heightened aggression was always likely. Moreover, Western leaders aren’t exactly deterring him…

If we chose to cede Ukraine, we should do so honestly, by strengthening economic sanctions on Russia but ending the pretension that we’ll do anything else. At a moral level, it’s fair to ask why we should do more: If European nations don’t care enough (the UK included) to invest in their own defense, why should Americans? Nevertheless, our clarity of purpose is critical. In U.S. foreign policy, false resolve is far worse than honest disinterest. Clear disinterest in one area allows us to maintain our credibility elsewhere, but when we abandon our word, American credibility is gutted everywhere.

Of course, we’ll have to be equally honest if we escalate against Russia. For a start, we’ll have to drop the platitudes and accept that confronting Russia carries real risks. Believing Russia’s existential interests are at stake in Ukraine, and leading a proud but pained nation that craves respect (read David Greene and Angela Stent), Putin is ready for a fight. And let’s be clear, while we could ramp up sanctions (a full-spectrum denial of Russian financial access to Western markets, for example) or provide arms to the Ukrainian government, those options carry consequences. Were Ukraine to deploy any U.S.-provided arms east of the Dnieper River, our involvement in the war would cross a modern-day Rubicon. Russia might well launch a full-scale invasion toward Kiev; and, again, the old credibility question would once again rise to the fore. In that scenario, our only means of deterring Russia might be the large-scale deployment of American military forces to western Ukraine.