Biden has said that if Tehran resumed strict compliance with the 2015 nuclear agreement - under which Iran restrained its nuclear program in return for relief from economic sanctions - Washington would too.

"The president has made clear that he believes that through follow-on diplomacy, the United States seeks to lengthen and strengthen nuclear constraints on Iran and address other issues of concern. Iran must resume compliance with significant nuclear constraints under the deal in order for that to proceed," Psaki said in a briefing on Wednesday.

"We would expect that some of his earlier conversations with foreign counterparts and foreign leaders will be with partners and allies and you would certainly anticipate that this would be part of the discussions."

Former president Donald Trump abandoned the Iran nuclear deal in 2018 and Iran in return has gradually breached its key limits, building up its stockpile of low enriched uranium, enriching uranium to higher levels of purity and installing centrifuges in ways barred by the deal.

On Tuesday, Biden's nominee for secretary of state Antony Blinken said Washington did not face a quick decision on whether to rejoin the nuclear deal and the Democratic president would need to see what Iran actually did to resume complying with the pact.

Australian Associated Press