Joe Biden has promised a change in US policy on Iran, but the president-elect's room for manoeuvre with the Islamic republic is narrow, and time is running out.
While outgoing US President Donald Trump has declared Tehran his arch-foe and sought to isolate it globally, Biden has suggested he would offer it a "credible path back to diplomacy".
Unlike four years ago, the Iran issue, centred on fears it is seeking a nuclear bomb, was largely absent from campaigning for the 2020 US presidential election, and Biden's proposals on the subject are still rather vague.
His task of trying to reconnect with Tehran promises to be difficult as the confrontational approach under Trump has seen Iran's distrust of the Americans intensify.
Sworn enemies for more than 40 years, the US and Iran have twice come to the brink of war since mid-2019 amid soaring tensions over a landmark deal on Iran's nuclear programme agreed in 2015.
Trump unilaterally withdrew the United States from the pact in May 2018 and launched a "maximum pressure" campaign against Iran with sanctions that plunged its economy into a deep recession.
But Trump failed to achieve his ultimate goal of forcing Tehran to negotiate a "better deal", leaving the way open for Iran to boast of the "resistance" of its people to the American "Great Satan".
"We urgently need to change course," Biden wrote in September in an opinion piece that described Trump's Iran policy as a "dangerous failure" which in his view isolated the US and brought Iran "closer to a nuclear bomb".
In the 2015 deal with world powers Britain, China, France, Germany, Russia and the United States, Iran agreed to curb its controversial nuclear programme in exchange for a relaxation of international sanctions.
But in response to the reimposed US sanctions, the Islamic republic has since May 2019 reduced most of its key commitments to the accord.
The International Atomic Energy Agency says Iran has considerably stepped up its production of low-enriched uranium, but without increasing it to a degree that allows military use.
In the op-ed published by CNN, Biden wrote that he would "offer Tehran a credible path back to diplomacy" in order to bring Washington back into the 2015 nuclear deal.
Also read: Iran's President Hassan Rouhani says Biden-win a chance for US to 'compensate for mistakes'
But the US president-elect also vowed to be "tough on Iran", and said that his country's return would hinge on the Islamic republic coming back to "strict compliance with the nuclear deal".
While Iran insists the United States can return to the pact, it says the Americans must first make amends and lift all sanctions reimposed or instigated by the Trump administration.
Tehran says that this is the condition for its return to commitments under the nuclear accord.
In recent weeks, it has even reiterated that in order to re-enter the agreement, Washington should first compensate Iran for the damage caused by the US withdrawal and sanctions.
Under Biden, the United States has an opportunity to make up for its "previous mistakes," Iranian President Hassan Rouhani, whose election in 2013 allowed talks on the nuclear issue to resume after eight years of deadlock, said on Sunday.
Iran's foreign ministry said Monday that US policy makers must change their mentality, language and actions to signal Washington is "turning back from the wrong path and making up for the past".
But the window of opportunity is tight since less than five months separate Biden's inauguration on January 20 and an Iranian presidential election set for June 18.
The upcoming election, which comes after conservatives hostile to the nuclear deal swept Iran's parliamentary elections in February, could sound the death knell for the alliance of reformists and moderates around Rouhani.
Ellie Geranmayeh of the European Council on International Relations said it is up to the three European countries that are party to the nuclear deal to immediately step up talks with the three other nations in the accord besides the US.
"If the nuclear deal can be preserved until Biden's inauguration, then the Iran file presents a natural area for renewed transatlantic cooperation," the Iran specialist said in a note.
But she added: "It is also unclear whether Biden will be willing to lift sanctions that are unrelated to nuclear matters and that the Trump administration introduced deliberately in order to (make) it hard to return to the agreement."