"We had four issues as our red lines," but "two issues have been almost resolved," Hossein Amir-Abdollahian was quoted as saying by state news agency IRNA, adding that "two issues remain, including (an) economic guarantee".

He did not elaborate on the second issue.

Iran has been engaged in direct negotiations in Vienna to revive the deal, known formally as the Joint Comprehensive Plan of Action (JCPOA), with France, Germany, Britain, Russia and China.

The United States, which unliterally pulled out of the deal in 2018, is participating indirectly.

"If the American side fulfils our two remaining demands today, we will be ready to go to Vienna tomorrow," Amir-Abdollahian said.

More than 10 months of negotiations had brought the parties close to renewing the landmark accord.

But the talks were halted after Russia this month demanded guarantees that Western sanctions imposed following its invasion of Ukraine would not damage its trade with Iran.

Amir-Abdollahian's remarks come a day after his visit to Moscow where counterpart Sergei Lavrov said Russia had received the necessary guarantees from Washington on trade with Iran.