Iran rejects any change to nuclear deal: official

"We will not accept any changes, any interpretation or new measure aimed at limiting" the 2015 deal between Iran and major powers, said Ali Shamkhani, secretary of the Supreme National Security Council, in remarks carried by ISNA news agency. 

Shamkhani also warned European countries "against the temptation of playing at the same game as the Americans".

"The ballistic programme of the Islamic Republic of Iran, which has a defensive nature, will steadfastly continue," said Shamkhani, who is a close ally of supreme leader Ali Khamenei.

He made the remarks as he met with Yusuf bin Alawi, the minister responsible for foreign affairs in Oman, in Tehran on Saturday - a key Gulf ally of the US with close ties to Iran.

On Friday, senior US State Department official Brian Hook said that President Donald Trump wanted to reach a "supplemental" deal with the European signatories to the Iran nuclear deal.

This would cover Iran's ballistic missile programme, its regional activities, the expiration of parts of the nuclear deal in the mid-2020s and tighter UN inspections, Hook said.

"We are taking things one week at a time, we are having very good discussions in London, Paris and Berlin," Hook, recently ousted Secretary of State Rex Tillerson's chief of strategy, said.

"There is a lot we agree on and where we disagree we are working to bridge our differences," he said in Vienna.

The 2015 accord between Iran and the United States, Russia, China, France, Britain and Germany curtailed Iran's nuclear activities in exchange for sanctions relief.

Iran, which according to the UN atomic watchdog has been abiding by the deal since it came into force in January 2016, has repeatedly ruled out any changes to the agreement.

In January, Trump said that the nuclear deal must be "fixed" by May 12 or the United States will walk away.

The European parties to the agreement are desperate to save it and have been scrambling to find ways to persuade Trump not to rip it up.