Last week, the White House — in seeking to reassure the bipartisan group of senators still gunning for, at the very least, a legislative signal to Iranians that they will have zero foibles about increasing sanctions pressure should Iran fail to get a move on with those nuclear concessions they recently promised — announced that they planned to crackdown on a list of more than two dozen people and companies who’ve been pulling a run-around on current sanctions.

The Iranians, evidently, were unappreciative of the gesture, and so very rudely interrupted the talks going down in Vienna last week by pulling their diplomats to reconvene back in Tehran. As Reuters reports, those talks over a potential interim deal resumed on Thursday…

Iran and six world powers will resume talks in Geneva on Thursday about how to implement a landmark nuclear agreement, a week after Tehran broke off the discussions in anger at an expanding U.S. sanctions blacklist.

Under the November 24 interim accord, Iran will curb its disputed nuclear program in exchange for a limited easing of sanctions that are damaging its oil-dependent economy. …

Diplomats said the task was complicated but that progress had been made during the December 9-12 meeting in Vienna, even though differences remained. They said there was a real political will on both sides to carry out the agreement.

…but under a rather more downcast diplomatic outlook. Says the LA Times:

Three weeks after President Obama hailed a landmark deal to suspend most of Iran’s nuclear program for the next six months, the mood among U.S. officials about the next round of negotiations has shifted from elated to somber, even gloomy.

“I wouldn’t say [chances of success are] more than 50-50,” Obama said last week. U.S. officials are “very skeptical” that Iran will accept Western demands, said his lead negotiator, Wendy R. Sherman.

The shift, officials say, is the result of a growing recognition of the compromises each side must make to resolve the decade-old impasse over Western suspicion that Iran will someday try to build nuclear weapons and the Iranian demand that the sanctions crippling its economy be lifted. …

“We can now identify all the main issues involved in the final deal,” said David Albright, a former United Nations nuclear inspector who heads the nonpartisan Institute for Science and International Security in Washington. “That doesn’t mean we can resolve them.”

When talks resume next month, “we still don’t know which Iran is going to show up: the one that cooperates or the one that nickels and dimes you,” Albright said.

That ostensibly cooperative side of Iran, however, has some work to do if even just the possibility of new sanctions is enough for them to throw a hissyfit (if they have every intention of negotiating in good faith on their end of the deal, one might wonder why it would matter quite so much) — which is probably why the aforementioned group of senators is proceeding with new legislation undeterred:

A bipartisan group of senators is preparing to defy the White House by introducing new Iran sanctions legislation as early as Thursday or Friday that would increase pressure on Iran if it fails to meet its obligations under the interim deal signed last month.

“The bill is bipartisan, has growing support, and because of that growing support, it may take another day,” said Adam Sharon, spokesman for chairman of the Senate Foreign Relations Committee, Sen. Robert Menendez.

The Senate bill, which is being written by Menendez, D-N.J., and Sen. Mark Kirk, R-Ill., proposes future sanctions that go into effect only if Iran violates the interim deal or the deal falls apart, Sharon said in an e-mail.

“They still get their sanctions relief, no new penalties are passed by Congress, and all parties are given the space to keep negotiating,” he said.