Araghchi was responding to a comment made on Tuesday by the US top negotiator Steve Witkoff, who said Tehran must “stop and eliminate its nuclear enrichment” to reach a deal with Washington.

“We have heard contradictory statements from Witkoff, but real positions will be made clear at the negotiating table,” Araghchi said.

“We are ready to build trust regarding possible concerns over Iran’s enrichment (of uranium), but the principle of enrichment is not negotiable,” he said.

Iran and the US are due to hold a second round of talks in Oman on Saturday over Tehran’s escalating nuclear programme, with president Donald Trump threatening military action if there is no deal.

On Thursday, Araghchi will deliver a message from Iran’s supreme leader Ayatollah Ali Khamenei to Russian president Vladimir Putin on a trip to Russia, Iranian state media reported.

“Amidst important global developments, close, continuous and trusting communication between Iranian and Russian authorities will serve regional as well as international peace and stability,” Iran’s ambassador to Russia, Kazem Jalali, wrote on X.

The Kremlin on Tuesday declined to comment when asked if Russia was ready to take control of Iran’s stocks of enriched uranium as part of a possible future nuclear deal between Iran and the US.

The Guardian reported that Tehran was expected to reject a US proposal to transfer its stockpile of enriched uranium to a third country such as Russia as part of an agreement that Washington is seeking to scale back Iran’s nuclear programme.