The deal meant to curb Iran's nuclear programme has been moribund since the withdrawal of the United States under president Donald Trump in 2018.

The major powers are awaiting Tehran's response to a proposal submitted on July 26 by EU foreign policy chief Josep Borrell.

"The European Union's proposals are acceptable provided that they provide assurances to Iran on various points, related to sanctions and safeguards," as well as pending issues with the International Atomic Energy Agency (IAEA), IRNA said, quoting an unidentified Iranian diplomat.

Britain, China, France, Germany, Iran and Russia, as well as the United States indirectly, resumed talks on the nuclear accord last week, after a months-long hiatus.

The EU-coordinated negotiations to revive the so-called JCPOA began in April 2021 before coming to a standstill in March.

The EU said on Tuesday it expected Tehran and Washington to "very quickly" respond to a "final" text aimed at salvaging the 2015 deal.

The 2015 accord gave Iran sanctions relief in exchange for curbs on its atomic programme to guarantee Tehran could not develop a nuclear weapon -- something it has always denied wanting to do.

The IAEA has found traces of enriched uranium at three undeclared Iranian sites. The agency's board of governors in June censured Iran for inadequately explaining the discovery.

Iran wants the IAEA to move on from the question of the undeclared sites.

Iranian sources at the weekend insisted that the IAEA first "completely resolve" that "political" issue to clear the way for the nuclear deal to be restored.