The latter contingency is implausible, but there is a bipartisan effort in the United States to make it more likely. Until a few weeks ago it was widely believed that a Biden administration would move fast to repair the damage Donald Trump did by withdrawing from the 2015 treaty in which Iran promised no work on nuclear weapons for fifteen years, but not necessarily so.

Why did Trump pull out in the first place? Sheer spite, really.

All the world’s intelligence agencies, including the American ones, agreed that Iran was meticulously obeying the terms of the Obama-era treaty, but Trump was systematically destroying every achievement of the ‘black, foreign imposter’ who preceded him in the White House. If Obama had granted Americans eternal life, Trump would have tried to undo it.

Iran isn’t even asking for an apology, although it certainly deserves one. It just wants the United States to revoke the international sanctions that were ended by the treaty of 2015, but that Trump unilaterally re-imposed, against the wishes of all the other major powers (Britain, China, France, Germany, the European Union and Russia), in 2018.

That could be done in a day, and as soon as it was, promised Iran’s President Hassan Rouhan, Iran would return to compliance within hours. ‘Return’, because to motivate all the other signatories to press the United States to return to the treaty, Iran itself started a slow-paced series of departures from the treaty terms in mid-2019.

Iran didn’t rush into retaliation. It waited a year first, telling the European powers that it would go on observing the letter of the treaty if they allowed Iranian banks and oil companies to go on trading with them. The Europeans didn’t dare, knowing Trump would punish European banks and companies if they did that, so Iran was left holding the bag.

When Iran did start breaching the treaty terms, it did so slowly and with plenty of warning, one provision at a time, letting the inspectors watch what they were doing at every step: first raising the level of uranium enrichment from the treaty-agreed 3.67% to 4.5% in November 2019, then going to 5% a year later.

However, when the United States and Israel resumed their campaign of assassinations against senior Iranian military and scientific personnel last year – General Qassem Soleimani in January and the country's top nuclear scientist, Mohsen Fakhrizadeh, in November – Iran’s parliament took a hand.

Iran is a partially democratic country, and the parliament is currently dominated by conservatives who are fed up with President Rouhani’s long patience on this issue. Three months ago they legislated a series of deadlines by which Iran would have to breach more serious aspects of the treaty if the United States does not rejoin it.

The first of those deadlines, when Rouhani’s government will be obliged to block short-notice inspections by the International Atomic Energy Agency, is only a week away: 21 February. The Biden administration could head that off simply by declaring that it will return to the treaty without conditions, but it appears that the Trump stupidity is catching.

“Will the U.S. lift sanctions first in order to get Iran back to the negotiating table?” CBS News asked Joe Biden a week ago. “No,” he replied, and US State Department spokesman Ned Price later elaborated: “We continue to urge Tehran to resume full compliance with the [nuclear deal]...because that, for us, would open up the pathway for diplomacy.”

Trump may be gone, but realism has not yet found its way back to Washington. When the United States breaks a treaty for no good reason and plunges tens of millions of Iranians into poverty, it is not the victim’s duty to rescind all its countermeasures first in order to prove its good faith.

It would be easy to choreograph a dance in which Iran and the United States undo this confrontation step by step in unison, thus saving America’s face by never mentioning who caused it. But insisting the Iranians move first, as if they were the guilty ones, is a non-starter: they may not be two-year-olds, but they have their pride. They aren’t fully grown-up either.

What Biden really must not do is demand that Iran make more concessions beyond the 2015 treaty before he agrees to end sanctions. That was Trump’s game, and with all this talk about ‘opening up the pathway for diplomacy’ Biden is edging dangerously close to that.