The frost has begun to melt. President Joe Biden can be credited with Thursday’s remarkable forward movement in his country’s dealings with Iran.

He has pledged to restore Iran’s nuclear deal with the Western powers, one that Donald Trump had abandoned. Acutely aware of the imperatives of geopolitics, Mr Biden has offered to team up with the countries of Europe. This is reckoned to be the first substantial diplomatic effort with Tehran in more than four years and serves to fulfil one of Mr Biden’s critical campaign promises. It bears recall that the US administration had backed away from Trump’s effort to restore sanctions on Iran, a drastic step that had alienated Washington from its allies in Europe.

Mr. Biden said he would lift sanctions imposed by President Trump only if Iran returns to the limits on nuclear production that it observed until 2019. The announcement will open what is likely to be a delicate set of diplomatic offerings. There are contretemps across the trail. The United States has no indication whether Iran will accept the offer; it has cautioned that the prospect of a meeting was a first step in what would be a lengthy, difficult process towards restoring the nuclear deal.

It is imperative that Iran return to full compliance with the deal, as the Biden administration has insisted. This must happen before the United States unwinds several economic sanctions that Mr.Trump had imposed, crippling the Iranian economy. Until then, and as a goodwill gesture, the Biden administration withdrew a demand that the Security Council enforce international sanctions against Iran for violating the original 2015 agreement that limited its nuclear programme.

Nearly every other nation had rejected the Trump administration’s insistence that the United States could invoke the so-called “snap back sanctions” because it was no longer a part of the accord. Additionally, the Biden administration is lifting travel restrictions on Iranian officials who seek to enter the United States to attend UN meetings. Should the President’s paradigm shift materialise, it will signify a major change in US foreign policy. Iran has advanced a guarded response.

The Iranian foreign minister, Mohammad Javad Zarif, said on Twitter that Tehran was waiting for American and European officials to “demand an end to Trump’s legacy of #EconomicTerrorism against Iran.” With Joe Biden in the White House, it is fervently to be hoped that terrorism will gradually lose its economic dimension. Equally, the comity of nations will expect Iran, pre-eminently its supreme leader, Ayatollah Khamenei, to soften its agenda on nuclear proliferation. There can be no meaningful diplomatic engagement if matters nuclear overshadow the equation. America’s approach has been rational enough. So too must Tehran’s.