The longtime adversaries have held three rounds of talks aiming for a deal on the programme, which the West believes is intended to develop nuclear weapons -- an allegation Tehran denies.

The talks, which began on April 12 and are mediated by Oman, are the highest-level contact in years between the two sides.

"The next round of negotiations will take place in Rome," Foreign Minister Abbas Araghchi said after a cabinet meeting on Wednesday.

The top diplomat said Iranian officials would also meet on Friday with representatives from Britain, France and Germany -- all parties to the 2015 nuclear deal.

The deal called for the lifting of sanctions in exchange for curbing Iran's nuclear activities, but fell apart when Washington withdrew from it in 2018 during Donald Trump's first term as US president.

After France threatened that the European trio could reimpose sanctions, Iran's UN mission said that "threats and economic blackmail" were "entirely unacceptable".

"Genuine diplomacy cannot proceed under threats or pressure," the diplomatic mission said in a letter carried Wednesday by Iran's ISNA news agency.

Trump sent a letter in March to Iran's supreme leader Ayatollah Ali Khamenei urging talks and warning of possible military action if Iran refused.

Since he returned to office in January, Trump revived his "maximum pressure" sanctions campaign, mirroring his approach during his first term.

Tehran has insisted that the ongoing talks should be solely focused on the nuclear issue and the lifting of sanctions.

During the last round in the Omani capital Muscat on Saturday, both sides reported progress.