Iranian President Hassan Rouhani spoke with French counterpart Emmanuel Macron on Saturday, warning him Iran would take the next step in reducing its nuclear commitments unless Europe lives up to its own undertakings.

Tensions have spiked in the Gulf since May last year when President Donald Trump unilaterally withdrew the US from a nuclear deal between Iran and world powers - known formally as the Joint Comprehensive Plan of Action (JCPOA).

The escalation has seen ships attacked, drones downed and tankers seized in the Strait of Hormuz, a chokepoint for around a third of the world's sea-borne oil.

At the height of the crisis, Trump ordered strikes against Iran on June 21 before cancelling them at the last minute.

Macron has been leading efforts to de-escalate the situation, and expressed hopes at a G7 meeting last week of bringing Rouhani and Trump together for a meeting.

But Rouhani has played down the likelihood of that happening unless the US first lifts crippling sanctions that it has slapped on Iran since pulling out of the deal.

"If Europe cannot operationalize its commitments, Iran will take its third step to reduce its JCPOA commitments," Rouhani told Macron in a phone call, quoted by the government website.

However, "this step, just like the other ones, will be reversible," he added.

"Unfortunately after this unilateral move by the US, European countries did not take concrete measures to implement their commitments.

"The contents of JCPOA are unchangeable and all parties must be committed to its contents," he said.

Rouhani said Iran had two priorities: for all parties to the JCPOA to fully implement their obligations and "securing the safety of all free maritime transportation in all waterways including the Persian Gulf and Strait of Hormuz."