The final days of one-term US President Donald Trump ought to have ushered in calm anticipation of an improvement in poisonous US-Iran relations . Instead, tensions are running high amid fears that either side, or Trump’s close friend Israel, might cause or seize on provocation and spark a regional security crisis. There have been potential triggers, symbolic and real. Following the assassination last November of senior Iranian nuclear scientist Mohsen Fakhrizadeh , for which Tehran blames the Jewish state, Iran told the UN’s nuclear watchdog on New Year’s Day that it would “produce enriched uranium with 20 per cent purity”, contrary to its undertakings under the 2015 Iranian nuclear deal. And Sunday was the first anniversary of the American assassination of Qassem Soleimani, the former commander of the Quds Force of the Islamic Revolutionary Guards Corps. Iran has repeatedly vowed to punish the perpetrators, and warned the United States to expect an attack from within “your own house”. Is US-Iran clash coming before Trump leaves office? No wonder tension between Washington and Tehran has prompted the world to count the days to the end of the Trump administration and the prospect of rehabilitation of the Iran nuclear deal negotiated with China, Russia and their European partners – so recklessly repudiated by Trump as “the worst deal ever” without any evidence of non compliance. US president-elect Joe Biden has vowed to rejoin the pact, but he does not take office until January 20. Meanwhile, the tension could strengthen the hand of hardline factions in Iran trying to prevent diplomacy with the West. Complex forces are at work. Many Europeans are keen for the US to go back to the nuclear negotiating table and Biden wants to form a coalition with European powers before addressing fragile relations with China. Trump has stepped up air and naval military activity in the Persian Gulf, which has done nothing to dampen fears of a strike. Apart from signalling a new approach, Biden cannot be expected to make any definitive moves on Iran perhaps for months while he recalibrates American foreign policy shaken up and confused by Trump. But that should not prevent him unequivocally reaffirming intention to rejoin the nuclear deal and a willingness to engage.