Western countries participating in the Iran nuclear deal have warned Tehran of serious consequences after it threatened to violate its terms.

Iran has announced it is scaling back curbs to its nuclear program under a 2015 deal with world powers, threatening to do more – including enriching uranium to a higher level – if countries did not shield it from US sanctions.

The UK, France and Germany said they would remain in the deal as long as Iran upheld its commitments, but said there would be “consequences” if Iran went further with its threats.

A year after Washington pulled out of the nuclear deal with Iran, President Hassan Rouhani unveiled measures that do not appear to violate the deal’s terms yet, but could do so in the future if Iran were to persist on the course he set out.

Under the nuclear deal, Iran is permitted to stockpile limited amounts enriched uranium and heavy water produced in that process, exporting any excess.

Mr Rouhani said Tehran would halt a program to sell excess enriched uranium and heavy water to other countries.

More importantly, he further threatened that in 60 days Iran would resume enrichment of uranium beyond the low level permitted under the deal, unless the five other powers signed up to it find a way to protect Iran’s oil and banking industries from US sanctions.

“If the five countries came to the negotiating table and we reached an agreement, and if they could protect our interests in the oil and banking sectors, we will go back to square one,” Mr Rouhani said.

“The Iranian people and the world should know that today is not the end of the JCPOA [Joint Comprehensive Plan of Action],” he said, using the acronym for the nuclear deal.

“These are actions in line with the JCPOA.”

In 2018, Mr Rouhani warned the US President to not ‘play with the lion’s tail’. Photo: Getty

Mr Rouhani’s announcement was met by new sanctions on Iran’s iron, steel, aluminum and copper sectors by the US.

In a statement, US President Donald Trump warned that “Tehran can expect further actions unless it fundamentally alters its conduct.

“The 2015 deal was signed between Iran, the United States, Russia, China, Britain, France and Germany.

Iran agreed to curbs on its nuclear program in return for the lifting of sanctions.

Washington’s European allies opposed President Donald Trump’s decision to pull out.

They have tried to find ways to blunt the economic impact of new US sanctions in the hope of persuading Tehran to continue to abide by it.

However, their efforts have largely failed, with all major European companies abandoning plans to do business with Iran for fear of US punishment.

France’s defence minister Florence Parly said she wanted to keep the nuclear deal alive and warned Iran it could face more sanctions if it did not honour its part of the deal.

“Today nothing would be worse than Iran, itself, leaving this agreement,” Ms Parly told BFM TV.

China said the agreement should be implemented and called on all sides to avoid an escalation of tensions.

The weeks leading up to the anniversary of MrTrump’s withdrawal from the agreement have seen a sharp tightening of US sanctions and an increase in tensions on other fronts.

From this month, Washington has effectively ordered countries around the world to stop buying any Iranian oil or face sanctions of their own, revoking waivers that had allowed some countries to continue buying Iranian oil. It says it aims to reduce Iranian crude exports to zero.

Washington has also blacklisted Iran’s Revolutionary Guards force as a terrorist organisation and Iran responded with threats to close the Persian Gulf’s Strait of Hormuz if its ships were blocked there.

Washington announced the deployment of an aircraft carrier to the Gulf to counter what it says are Iranian threats.

Tehran says the USS Abraham Lincoln is replacing another carrier that had already left the area under a scheduled rotation, and calls the announcement “psychological warfare” based on old news.

-with AAP