The US has agreed to the idea of taking part in talks involving Iran and world powers with a view to reviving a landmark nuclear deal.
Iran vowed to limit its nuclear programme in return for the lifting of economic sanctions under the 2015 deal.
But former President Donald Trump withdrew the US from the deal in 2018, leading Iran to roll back commitments.
Now the US has expressed intent to rejoin the deal under President Joe Biden.
On Thursday, the Biden administration made its firmest pledge yet to re-engage with Iran over the deal, known as the Joint Comprehensive Plan of Action (JCPOA).
State department spokesman Ned Price said the US would accept an invitation from the European Union to meet Iran for talks.
Iran has ratcheted up pressure on the Biden administration, threatening to block international inspections of its nuclear sites within days if the US does not lift sanctions.
Since the US withdrew from the deal, Iran, which says its nuclear programme is peaceful, has resumed or begun nuclear activities barred under its terms. This has heightened concern among the parties to the deal, who suspect Iran’s intentions.
In response, the US and its European allies – the UK, France and Germany – have called on Iran to refrain from blocking inspections, warning jointly that the move would be “dangerous”.
On Thursday, the four powers said they shared a commitment to ensuring Iran could “never develop a nuclear weapon”.
Suspicions that Iran was using its nuclear programme as a cover to develop a nuclear bomb prompted the EU, US and UN to impose sanctions in 2010.
In 2015, Iran reached a deal with six powers – the US, UK, France, China, Russia and Germany – that saw it limit its nuclear activities in return for sanctions relief.
Under the terms of the deal, Iran agreed to limit its uranium enrichment and allow international inspectors to access sites and facilities.