President Obama and Iranian President Hassan Rouhani spoke by phone on Friday, an event greeted with unbounded — and inadvisable — enthusiasm by the chattering class.

The substance of the call and the president’s remarks afterward were deeply worrisome. Whenever the president parrots the idea that the problem is “mistrust” between the parties — one an open democracy and the other a theocratic dictatorship — you know it’s trouble. In doing so, the president merely reinforces Iranian propaganda that we bear equal responsibility for this “mistrust.”

Even worse was Obama’s echoing the Iranian deception that it can’t possibly be pursuing nuclear weapons because “Iran’s supreme leader has issued a fatwa against the development of nuclear weapons.” It is frightful to imagine Obama takes seriously Iran’s deceitful line.

The problem is not that Iran “mistrusts” us or that there is some religious prohibition on nuclear weapons; it is that the mullahs’ regime sponsors terror, helps kill Americans, threatens its neighbors, represses its people, holds Americans against their will and violates sanctions prohibiting development of nuclear weapons.

Worse still was the administration flacking on behalf of the Iranian dictatorship. Former White House aide and Obama super PAC head honcho Bill Burton tweeted indignantly that it was wrong to call Rouhani a Holocaust denier. A White House spokesman said it was a positive sign that the Iranians were using social media. (For propaganda, we should note; their citizens are not afforded that right.) The Obama team’s willingness to take the bait and hold on tightly has been quite remarkable.

What we see on the part of the U.S. government is undisguised desperation for a deal. The United States will leave the repressive regime alone (Obama said the Iranians can stop worrying about regime change) and even allow Tehran the right to pursue a peaceful nuclear program. Obama, as on Syria, needs an agreement from Iran to calm calls for action; the contents matter far less than the existence of a deal.

The Iranians demand the right to enrich uranium and a lifting of sanctions. One suspects the Obama administration will cave on these points. Before the telephone call, Congress was poised to move forward with additional sanctions to put the mullahs’ feet to the fire. We wonder if the call was staged to hold that off and whether the administration, as it has done in the past, will try to slow Congress down. We have a dialogue now! Can’t spoil the good mood, you see.

Congress should be resolute. Unless and until there is an airtight deal, Congress should refuse to lift sanctions and should tighten the conditions under which Obama is permitted to waive sanctions. In refusing to vote for authorization of the use of force against Syria, Iran’s junior partner, and its use of weapons of mass destruction, lawmakers on the right and left contributed to an impression of unseriousness and, no doubt, emboldened Iran. They have an obligation to reverse that impression.

Jennifer Rubin is a columnist for The Washington Post.