A senior advisor to Iran's supreme leader says Tehran could boost its uranium enrichment to "five percent" even as a top Iranian cleric warns Britain should be "scared' of Tehran's response over oil tanker capture in Gibraltar.

President Hassan Rouhani visits the Bushehr nuclear power plant just outside of Bushehr, Iran. (File)
President Hassan Rouhani visits the Bushehr nuclear power plant just outside of Bushehr, Iran. (File) (AP)

A top advisor to Iran's supreme leader has hinted Tehran could boost its uranium enrichment to five percent for "peaceful" aims, ahead of deadline it set for world powers to save a landmark 2015 nuclear deal.

Iran is acting on its May 8 threat to suspend from Sunday [July 7] parts of the agreement in response to US President Donald Trump's reimposition of crippling sanctions after unilaterally withdrawing from the deal in May last year.

The signal comes as Tehran is engaged with London in a rift over the seizure of Tehran's oil tanker at Gibraltar on Thursday with an Iranian cleric warning UK on Saturday about possible retaliation.

Macron warns of consequences

French President Emmanuel Macron warned his Iranian counterpart on Saturday that he was deeply concerned by any further weakening of the 2015 nuclear deal and warned that consequences would follow.

Macron, who was speaking to Iranian President Hassan Rouhani, said he wanted to push dialogue between now and July 15 to bring all sides back to the negotiating table.

"The president recalled his deep concern in the face of the risk of a new weakening of the 2015 nuclear accord, and the consequences that would necessarily follow," a statement from the French presidency said.

Uranium enrichment threat

The 2015 accord capped Iran's enrichment maximum at 3.67 percent, sufficient for power generation but far below to more than 90 percent level required for a nuclear weapon.

Uranium enrichment "will increase as much as needed for our peaceful activities," Ali Akbar Velayati, international affairs advisor to Supreme Leader Ayatollah Ali Khamenei said in an interview published on Friday on the leader's official website.

"For Bushehr nuclear reactor we need five percent enrichment and it is a completely peaceful goal," he added.

Bushehr is Iran's only nuclear power station and is currently running on imported fuel from Russia that is closely monitored by the UN's International Atomic Energy Agency.

Failure by EU and US sanctions

On May 8, Iran announced it would no longer respect the limits set on the size of its stockpiles of enriched uranium and heavy water, and threatened to abandon further nuclear commitments, including exceeding the agreed uranium enrichment maximum from July 7.

It has also threatened to resume building from that date a heavy water reactor –– capable of one-day producing plutonium –– in Arak in central Iran, a project that had been mothballed under the deal.

The move comes in response to what Iran deems a failure by the remaining parties to the deal –– Britain, China, France, Germany, and Russia –– to provide Tehran with relief from the US sanctions.

"The US has directly and Europeans indirectly violated" the deal, said Velayati.

"We will react proportionally the more they violate it."

UK should be 'scared' of Iran's response

Britain should be "scared" about Tehran's possible retaliation for the capture of an Iranian supertanker by Royal Marines in Gibraltar, the Fars semi-official news agency on Saturday reported an Iranian cleric as saying.

"I am openly saying that Britain should be scared of Iran's retaliatory measures over the illegal seizure of the Iranian oil tanker," said Mohammad Ali Mousavi Jazayeri, a member of the clerical body the Assembly of Experts.

"We have shown that we will never remain silent against bullying ... As we gave a staunch response to the American drone, the appropriate response to this illegal capture (of the tanker) will be given by Iran as well," he said.

We spoke with our Iran analyst Mariam Babakhanians for more details.

Tehran's fury over Grace 1 capture

British Royal Marines seized the supertanker Grace 1 on Thursday for trying to take oil to Syria in violation of EU sanctions in a move which drew Tehran's fury and could escalate its confrontation with the West.

Iran downed a US military drone on June 20 that it said was flying over one of its southern provinces on the Gulf. Washington said the drone was shot down over international waters.

An Iranian Revolutionary Guards commander threatened on Friday to seize a British ship in retaliation for the capture of an Iranian supertanker.

Source: AFP