WASHINGTON: Secretary of State John Kerry will this week defend an emerging deal intended to curb Iran’s nuclear ambitions, urging skeptical US lawmakers not to put up obstacles that could scupper the tough negotiations.

“I’ll lay out the facts,” Kerry told CBS’s “Face the Nation” on Sunday when asked about a different narrative emerging from Iranian leaders about the outlines of a deal agreed in Lausanne, Switzerland earlier this month.

“Everything I have laid out is a fact. And I’ll stand by them.”

The Lausanne framework marked a major breakthrough in a 12-year standoff between Iran and the West, which disputes Tehran’s denial that it is seeking to acquire nuclear bomb.

Kerry, however, has come under fire from US lawmakers, including his former Republican Senate friend and adversary John McCain who last week said America’s top diplomat was “delusional.”

“I think you’re going to find out that they never agreed to the things that John Kerry claimed they had,” McCain told a radio show on Thursday, adding that Kerry was now trying to “sell a bill of goods hoping that maybe the Iranians wouldn’t say much about it.”

But President Barack Obama on Saturday leapt to Kerry’s defense.

Suggesting America’s top diplomat was “somehow less trustworthy in the interpretation of what’s in a political agreement than the supreme leader of Iran — that’s an indication of the degree to which partisanship has crossed all boundaries,” Obama told reporters in Panama.

Obama said he could understand that people might not trust Iran, which has not had diplomatic ties with the United States since the 1979 storming of the US embassy in Tehran.