The EU and world powers are scrambling to try to get negotiations in Vienna aimed at reviving the 2015 accord back on track after the election of a hardliner in Tehran.

Iran's chief negotiator on the deal, Deputy Foreign Minister Ali Bagheri, wrote on Twitter that he would be in Brussels on Wednesday "to continue our talks on result-oriented negotiations".

EU spokesman Peter Stano said the meeting would involve the bloc's lead negotiator Enrique Mora, who visited Tehran earlier this month to push Iran to restart full negotiations.

Stano said the EU's diplomatic service was "sparing no efforts to resume talks of all parties in Vienna".

In Washington, State Department spokesman Ned Price said the United States was "very supportive" of the EU engagement.

"That said," he told reporters, "the ultimate destination needs to be Vienna."

The agreement between Iran and world powers to find a long-term solution to the now two-decade-old crisis over its controversial nuclear programme has been moribund since former US president Donald Trump walked out of the deal in May 2018 and imposed sweeping sanctions.

His successor Joe Biden has said he is ready to re-enter the agreement, so long as Iran meets key preconditions including full compliance with the deal whose terms it has repeatedly violated by ramping up nuclear activities since the US left the pact.

But the Vienna-based talks through intermediaries made little headway, before being interrupted by the election of hardliner Ebrahim Raisi as Iran's president and suspended for the last four months.

The US pointman on Iran, Rob Malley, earlier Monday renewed a warning that the United States had "other options" if Iran's nuclear work advances although he said the Biden administration preferred diplomacy.

The EU acts as coordinator for the deal that also involves Britain, France, Germany, China and Russia.