As the Middle East burns, Russia’s assault on Ukraine’s freedom is at its most critical juncture since Vladimir Putin’s annexation of Crimea in March. Anders Fogh Rasmussen, the NATO secretary general, has warned the alliance that Putin could decide to send thousands of troops across the Ukrainian border to liberate besieged ethnic Russian militias in Donetsk. If Putin takes that step, the United States and Europe will likely respond by imposing Draconian sanctions on Russia. That will deepen the Cold War-like freeze between Moscow and the West for many years.

Obama faces a delicate and difficult balancing act with the Kremlin. On the one hand, he must deter further Russian adventurism in Ukraine through sanctions and international isolation of the Russian government. On the other, he needs to find a way to remain engaged with Putin on issues vital to us — nuclear stability between the United States and Russia, keeping nuclear materials out of the hands of terrorists, as well as cooperation on Iran and Afghanistan. This will test the administration’s diplomatic skill, but there is no practical alternative.

There is growing globally a political narrative, fair or unfair, that the United States no longer leads with as much confidence as it once did in Europe, the Middle East, and Asia. Iran’s leaders, as well as a newly assertive China, will be watching to see whether Obama can restore American power and credibility in the Middle East and Russia crises.

Obama needs to move quickly on both.