Iran has agreed to discuss proposals to limit its uranium enrichment at talks in the next week in Moscow over its nuclear program.

A tense exchange of letters between EU diplomats, who deal with Iran on behalf of the six powers, and Iranian officials had earlier appeared to suggest Tehran may be backtracking on its expressed willingness to discuss their most pressing concern – high-grade uranium enrichment even in broad terms.

But on Monday, Iran’s chief nuclear negotiator Saeed Jalili agreed to focus on the six powers’ demands at the Moscow meeting, during a one-hour phone conversation with EU foreign policy chief Catherine Ashton.

“The Iranians agreed on the need for Iran to engage on the (six powers’) proposals, which address its concerns on the exclusively peaceful nature of the Iranian nuclear program,” a spokesman for Ashton said.

The negotiations, which had been taking a negative turn of late, will probably focus on the elimination of the production of highly enriched uranium, above 20%. This is something that Iran agreed to years ago, with a fuel swap between them and another country, so the uranium gets enriched elsewhere. But that was rejected, in favor of a proposal that the P5+1 (permanent five members of the Security Council plus Germany) could better control.

Meanwhile, the Senate, being as helpful as ever, sent a bipartisan letter asking the Administration to basically not negotiate during the negotiation.

Authored by Sens. Robert Menendez (D-NJ) and Roy Blunt (R-MO), the draft letter outlines the “absolute minimum steps” Iran must take in Moscow: shutting down its Fordow enrichment facility, ending enrichment of uranium to high levels, and shipping out its stockpile of high-enriched uranium. The letter says that Iran’s agreement to these steps would “justify continued discussions,” but doesn’t outline any other possible concessions.

While that leaves the door open for other possible lesser concessions, the Senators rule out acceding to a key Iranian goal until Iran agrees to the full spectrum of Western and U.N. demands.

So as the Administration goes to Moscow, the Senate is trying to shut down any possible concessions, and even larding on additional sanctions. Basically the hardliners in the US are trying whatever they can to muck up negotiations. If we get anything out of Moscow it’ll be a miracle.