"Sanctioning a foreign minister means failure in talks", Zarif said. The identity of the vessel and the nationality of the crew are not known.
The Royal Navy will join a US-led taskforce to protect merchant ships travelling in the Gulf.
Iran recently began surpassing uranium enrichment limits set in the 2015 deal, but says these moves can be reversed if given enough economic incentives to offset USA sanctions.
The US is acting alone against Tehran and its allies are too "ashamed" to join its forces in the Gulf, Iran's top diplomat said Monday, dismissing Washington's calls for talks as a sham.
Britain said the seizure was in retaliation for its stopping an Iran oil tanker in the waters off Gibraltar that it said was smuggling oil to Syria in early July.
Our approach to Iran hasn't changed.
In response, the United States ambassador on disarmament Robert Wood said: "Iran simply needs to make up its mind to decide what it wants to do".
"The Persian Gulf is like a tinderbox and explosion of the first firecracker can lead to a huge disaster".
Attacks on Saudi tankers and other vessels off the UAE coast, Iran's downing of a United States surveillance drone, and a plan for U.S. air strikes on Iran last month-that Trump called off at the last minute-increased fears of a war in the region.
Tensions between Iran and its arch-foe the United States have soared since Trump announced a year ago that the USA was withdrawing from the deal and began reimposing sanctions against the Islamic republic.
"I'm very sceptical about that [US-led mission], and I think that's a scepticism that many others share", Olaf Scholz, Germany's vice chancellor and finance minister, told ZDF television last week.
"They thought Iran's system is weakened", he said.
"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". "We remain committed to working with Iran and our global partners to de-escalate the situation and maintain the nuclear deal".
It has threatened to block all exports via the Strait, through which a fifth of global oil traffic passes, if other countries comply with USA pressure to stop buying Iranian oil.
"The upcoming weeks will see whether the Iran nuclear deal can be saved".
Iran said it had increased its stockpile of heavy water beyond the 130-ton limit, according to Behrouz Kamalvandi, a spokesman for the Atomic Energy Organization of Iran.
Trump reportedly sided with Treasury Secretary Steven Mnuchin, who argued that the administration should renew sanctions waivers.
Naval forces of the Islamic Revolutionary Guard Corps "seized this ship around Farsi Island which was carrying around 700,000 litres of smuggled fuel", said a Guards statement quoted by the official news agency IRNA.
"Iran used to forgo some maritime offences in ..."
It follows a spate of incidents - including the seizure of ships - between Iran and Western powers, in particular Britain and the USA, centered on the vital Strait of Hormuz thoroughfare.
Britain repeatedly ruled out any exchange and has since been giving UK-flagged vessels in the region a naval escort. Brig Gen Ramezan Zirahi, an IRGC commander, said their boats had been patrolling the Gulf to control traffic and detect illicit trade when they seized the tanker.
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