An oil tanker is seen after it was attacked at the Gulf of Oman, in waters between Gulf Arab states and Iran, June 13, 2019. - REUTERS

Iran has vowed to scale back its nuclear commitments as regional tensions flared over last week’s tanker attack, with both the US and UK pointing the finger at Tehran.

The semi-official Tasneem news agency said Iran’s Atomic Energy Organisation would on Monday announce the measures Tehran has taken to dial back its international obligations under the terms of the now-crumbling 2015 nuclear deal.

Those measures include moves to increase both stocks of enriched uranium and the production of heavy water at the Arak nuclear complex, a site Iran has barred international watchdogs from visiting since 2008.

Both measures would nullify some of the key tenets of the nuclear accord, which offered economic incentives in exchange for the cessation of activities that might lead Tehran to build a nuclear weapons capability.

The announcement was foreshadowed last month when Iran threatened to walk back its nuclear commitments if the international community failed to contain the impact of US sanctions applied by Washington after it pulled out of the deal.

But the accelerated timing appears to be a consequence of last Thursday’s tanker attack and its fallout.

Tehran denies any role in the explosions that ripped through two oil tankers in the Strait of Hormuz, damaging the Japanese-owned Kokuka Courageous and the Norwegian-operated Front Altair.

The US military on Friday released video footage it said showed an Iranian patrol boat removing an "unexploded limpet mine" from the Kokuka Courageous, which was carrying highly flammable methanol when it was hit by two blasts.

According to the ship’s owner, crew on board noticed a “flying object” before the second blast.

Mike Pompeo, the US Secretary of State, blamed Iran, citing “intelligence, the weapons used, the level of expertise needed to execute the operation, recent similar Iranian attacks on shipping, and the fact that no proxy group operating in the area has the resources and proficiency to act with such a high degree of sophistication.”

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US President Donald Trump said the attack had “Iran written all over it”.

The speaker of Iran’s parliament hit back on Sunday, saying that Washington could be to blame for the “suspicious” attacks.

Meanwhile the US’s top Middle East ally Saudi Arabia used an op-ed column to call on the international community to take a “decisive stance” against what Crown Prince Mohammad bin Salman termed “expansionism” by his regional arch-rival.

“We will not hesitate to deal with any threat to our people, our sovereignty and our vital interests,” the crown prince and kingdom’s day-to-day leader wrote.

But Japanese Prime Minister Shinzo Abe, who was in Iran meeting with Supreme Leader Ayatollah Ali Khamenei when the tankers were attacked, is understood to want more evidence.

Mr Abe was in Tehran on an unprecedented goodwill mission, aimed at defusing tensions between Washington and the Islamic Republic.

An official with Japan’s Foreign Ministry said the prime minister disputed Mr Pompeo’s assessment that only Iran could have carried out the attack, noting that the US and Israel also possessed the required capabilities.

“Japan adamantly condemns the act that threatened a Japanese ship, no matter who attacked,” Mr Abe said, reiterating that Japan urged “all related countries” to avoid an accidental confrontation in the region.

But yesterday’s announcement from Iran’s nuclear agency has raised both the tensions and the stakes of regional confrontation.

Jeremy Hunt, the Foreign Secretary, warned there was a "great risk" of escalation in the region. "Both sides in this dispute think that the other side wouldn't want a war,” he said.