Nearly half the senate is urging President Obama not to allow the Iranians to run out the clock on their nuclear program by endlessly negotiating while surreptitiously building a bomb.

The Cable:

Nearly half the Senate told President Barack Obama today that unless Iran gives three specific concessions at this weekend's talks with world powers in Moscow, he should abandon the ongoing negotiations over the country's nuclear program.

"It is past time for the Iranians to take the concrete steps that would reassure the world that their nuclear program is, as they claim, exclusively peaceful," wrote 44 senators in a Friday bipartisan letter organized by Sens. Robert Menendez (D-NJ) and Roy Blunt (R-MO). "Absent these steps, we must conclude that Tehran is using the talks as a cover to buy time as it continues to advance toward nuclear weapons capability. We know that you share our conviction that allowing Iran to gain this capability is unacceptable."

The senators wrote that the "absolute minimum" Iran must do immediately to justify further talks is to shut down the Fordo uranium enrichment facility near Qom, freeze all uranium enrichment above 5 percent, and ship all uranium enriched above 5 percent out of the country.

"We understand that this was the very proposal that the P5+1 advanced during the Baghdad meeting," the senators wrote, referring to the permanent five members of the U.N. Security Council plus Germany. "Were Iran to agree to and verifiably implement these steps, this would demonstrate a level of commitment by Iran to the process and could justify continued discussions beyond the meeting in Moscow."

Josh Rogin believes there should be "confidence building measures" offered by the west in exchange for Iran's agreement on the three conditions. Ordinarily, and if negotiations were being held in good faith, that might be a great idea.

But it is Iran who needs to establish itself as a reasonable, honest partner. The west hasn't been lying about its intentions. They haven't sought to cover up what they've been doing. It is Iran who has spent the last decade denying their intent to build a nuclear weapon despite mountains of evidence to the contrary.

First, Iran must prove its good faith by agreeing to those three conditions. After they have been verifiably implemented, then we can start talking about western "confidence building measures."

That should be a minimum for continued negotiations.