After Trump, what will Biden do about Iran?
US President-elect Joe Biden says the international system is "coming apart at the seams".
He's promised to salvage America's reputation and says he's in a hurry. "There will be no time to lose," he wrote in Foreign Affairs magazine earlier this year.
On his long to-do list is a pledge to rejoin the 2015 Iran nuclear deal - the Joint Comprehensive Plan of Action (JCPOA), to give it its formal title - one of the signature, if hotly debated, achievements of Donald Trump's predecessor in the White House, Barack Obama.
Since withdrawing from the deal in May 2018, President Trump has been doing his utmost to demolish it.
But despite more than two years of Mr Trump's policy of "maximum pressure" on Iran, the Islamic Republic has not buckled and is closer to acquiring the technology needed for a nuclear weapon than it was when the US started to turn the screws.
Will Joe Biden, who takes office in January, return to the status quo ante? Given the passage of time and divided state of American politics, can he?
"The strategy is very, very clear," says Aniseh Bassiri Tabrizi, an Iran expert at London's Royal United Services Institute (Rusi). "But it won't be easy."
'No going back'
It's fair to say there are considerable challenges.
The complex web of US sanctions imposed over the past two years gives Mr Biden plenty of possible leverage, should he choose to use it. So far he's talked only in terms of Iran upholding its existing JCPOA obligations.
"Tehran must return to strict compliance," he wrote in January. But that's already a challenge. Following Donald Trump's exit from the JCPOA, Iran began to row back on its own commitments.
In its last quarterly report, the International Atomic Energy Agency (IAEA) said Iran had stockpiled about 12 times the amount of low-enriched uranium permitted under the JCPOA.
It had also started enriching uranium to higher purity than the 3.67% allowed under the deal.
Low-enriched uranium is used for many civilian nuclear-related purposes - but at its highest state of purification (which Iran is nowhere near, nor known to be pursuing) it can be used in a nuclear bomb, hence the concern. bbc