DUBAI — Iran runs security in the Strait of Hormuz and will no longer tolerate "maritime offenses" there, its foreign minister said on Monday, a day after it seized a second oil tanker near the strategic waterway that it accused of smuggling fuel.

Tanker traffic through the Strait has become a focus for an increasingly tense standoff between Washington and Tehran, into which Britain has also been dragged, and the United States has beefed up its military presence in the Gulf since May.

On Sunday, Iran's elite Revolutionary Guards Corps seized the Iraqi tanker north of the Strait and detained its seven crew, state media reported. Guards commander Ramezan Zirahi was quoted as saying it was carrying 700,000 liters of fuel .

"Iran used to forgo some maritime offenses in ... (the) Gulf but will never close (its) eyes anymore," Foreign Minister Mohammad Javad Zarif told a televised news conference in Tehran.

"... Iran is responsible for the security and safety of the Strait of Hormuz and the region."

Iran has threatened to block all exports via the Strait, through which a fifth of global oil traffic passes, if other countries comply with US pressure to stop buying Iranian oil.

Zarif criticized US sanctions imposed on him on Wednesday, saying Washington had closed the door to diplomacy over Iran's 2015 nuclear deal, which US President Donald Trump exited last year.

The deal with a handful of global powers had curbed Tehran's nuclear work in return for an easing of sanctions, striking a delicate political balance that the US pullout has destabilized.

Strains between Washington and Tehran have heightened further since the spring. In June, Iran's downing of a US drone prompted preparations for a US retaliatory air strike that Trump called off at the last minute.

Angered by intensified US sanctions designed to strangle its vital oil trade and the failure of European parties to agree on a way of salvaging the nuclear agreement, Tehran has scaled back its commitments under the pact.

"Iran will leave its 2015 nuclear deal with powers if necessary," Zarif said on Monday, adding that all measures taken by Iran were however "reversible if its interests under the deal are secured."

Iran has so far rejected calls by the Trump administration to negotiate a new deal.

He also labelled as "piracy" the seizure by Britain in July of an Iranian oil tanker near Gibraltar that London accused of violating sanctions on Syria.

Two weeks later, Iran's Revolutionary Guards seized a British tanker, Stena Impero, near the Strait of Hormuz for alleged marine violations.

"Britain has been complicit in the US economic terrorism against Iran," Zarif said. — Reuters