WASHINGTON (BLOOMBERG) - The Biden administration sought to dial back Iranian assessments that the two sides are getting close to an agreement on reviving the 2015 nuclear deal, saying disagreements remain wide on what steps they need to take to come back into compliance.

A senior State Department official, speaking to reporters on condition of anonymity, said the two sides are closer to the beginning of negotiations than to the end. The official spoke after a second round of talks in Vienna this past week in which the US and Iran didn't meet directly but negotiated through their European, Russian and Chinese partners.

The official's comments appeared intended to counter speculation of an impending deal after Iranian President Hassan Rouhani said the talks are 60 per cent-70 per cent complete and the two sides could soon resuscitate the Joint Comprehensive Plan of Action, which limited the scope of Iran's nuclear programme in exchange for the easing of economic sanctions.

President Donald Trump pulled out of the nuclear accord in 2018 - calling it the "worst deal ever" - and ramped up restrictions on the Islamic Republic, including on oil sales. Iran responded later by enriching uranium beyond agreed-upon limits, but insisting it remained a party to the nuclear accord.

The US declined to say which sanctions the Biden administration is prepared to lift, while making clear that terror-related restrictions imposed late in the Trump administration would likely be one target.

The official also said the two sides had made some progress in the talks and acknowledged that the US was open to different types of sequencing under which both nations would return to compliance with the deal.

In the past, President Joe Biden and his team have argued that the US would come back into compliance only after Iran did.