The UK must be responsible for the safety of its own ships in the Gulf, the US secretary of state, Mike Pompeo, has said.

His remarks reflect unresolved tensions between Britain and the US over Donald Trump’s plans for a US-led military taskforce to protect international shipping operating off the Iranian coast. The UK is meanwhile seeking to assemble a European naval protection force.

Speaking on Fox News, Pompeo said: “The responsibility in the first instance falls to the United Kingdom to take care of their ships. The US has a responsibility to do its part.”

He argued that the current crisis was not a result of US sanctions, but of longstanding Iranian malign behaviour in the region. “This is a bad regime; it’s not honouring the people of Iran,” he told the Fox & Friends television programme. “They’ve now conducted what amounts to national piracy – a nation-state taking over a ship that’s travelling in international waters.”

British ministers discussed the issue at a Cobra emergency meeting that largely focused on how to respond to the Iranian capture on Friday of the British-flagged Stena Impero. The ship, crewed largely by Indian nationals, is being held in the Iranian port of Bandar Abbas. All crew members are in good health and still onboard, the Iran embassy in India said on Monday.

The detention comes at a time of high tension in the region, with US, British and Iranian forces facing off at sea.

The UK foreign secretary, Jeremy Hunt, spoke to his German and French counterparts on Sunday to urge them to recognise the need to internationalise the maritime security operation in the Gulf.

The US has been seeking to recruit allies to take part in a coalition, known as Operation Sentinel, to protect the sea lanes. “We’ll build out a big coalition of countries all across the world to do that. We’ll ultimately be successful,” Pompeo told CBS News.

Hunt told parliament on Monday that he was seeking to develop a maritime protection mission with Germany, France and other European nations, but not including the US, because of their different agendas. The foreign secretary pointed out that the Europeans were not part of the US “maximum pressure” campaign on Iran.

Donald Trump said that recent events had made him less willing to do a deal with Tehran. “They put their finger up in the air and disrespected the United States. They shouldn’t have done that,” the president said. “Frankly it’s getting harder for me to make a deal with Iran because they behave very badly. They say bad things. I’ll tell you, it could go either way.”

A spokesman for the prime minister, Theresa May, said: “We already work closely with international partners to ensure a coordinated effort to defend freedom of navigation … The high volume of ships moving through the strait of Hormuz – up to 30 ships covering more than 100 nautical miles – makes it impossible to escort vessels individually”.

Timeline Recent tensions in the Gulf Show Hide Tensions between the US and Iran have soared in 2019, with Washington dispatching warships to the Gulf, and Tehran resuming higher uranium enrichment. The UAE says four commercial ships off its eastern coast 'were subjected to sabotage operations'. Yemen's Houthi rebels launch a drone attack on Saudi Arabia, striking a major oil pipeline and taking it out of service. Saudi Arabia subsequently blames Iran for the attack. A rocket lands near the US embassy in the Iraqi capital, Baghdad, without harming anyone. It's not clear who is behind the attack, but after the initial reports, Donald Trump tweets: 'If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!' Saudi Arabia says 26 people were wounded in an attack by Yemen's Houthi rebels on an airport in the kingdom's south-western town of Abha. Two oil tankers near the strategic strait of Hormuz were reportedly attacked in an assault that left one ablaze and adrift. 44 sailors were evacuated from both vessels and the US navy assisted. Iran’s Revolutionary Guards say they have shot down what they called a US 'spy' drone they claim was flying in in the country’s airspace. The US military confirm one of its drones has been taken down, but say it was in international airspace. Donald Trump reportedly gives approval for the US military to launch strikes on Iran in retaliation for the loss of the drone, before pulling back at the last minute. The Iranian and US presidents trade insults, with Hassan Rouhani suggesting that Donald Trump suffered from a “mental disorder” and Trump once more threatening Iran with “obliteration”. Iran summons UK ambassador over an incident off Gibraltar as Royal Marines seize a tanker, Grace 1, the UK suspects of carrying oil to Syria. The International Atomic Energy Agency, the body tasked with verifying Iranian compliance with the terms of the nuclear deal, verifies that Tehran has breached the agreed 3.67% limit for enriched uranium. The UK government says three Iranian boats were warned off by the frigate HMS Montrose after Iranian boats 'attempted to impede' a British oil tanker in strait of Hormuz. Tehran denies involvement. In a major escalation, Iran seizes the Stena Impero, a British-flagged tanker, off its coast. Iranian officials later make it clear that the capture was in retaliation for the capture of the Iranian supertanker Grace 1 earlier in July. Despite US attempts in the courts to prevent it, Gibraltar says it will free oil tanker at centre of the Iran row. Iran gives assurances the oil is not destined for Syria, where selling it would breach international sanctions against Britain accuses Iran of breaching those assurances after Tehran acknowledged the oil had been sold, and the reflagged tanker Adrian Darya 1, previously known as Grace 1, had reached its final destination after the ship was photographed off the coast of Syria.

About a fifth of the world’s oil passes through the Strait of Hormuz, the busiest shipping lane in the world for crude tankers, and it is less than 25 miles (40km) wide at its narrowest point. Tensions in the Gulf had already affected oil trading, and Friday’s tanker seizures caused prices to rise.

Britain has concerns that a US-led maritime security operation may have a different emphasis since Trump wants Europeans to join the US in pulling out of the nuclear deal signed in 2015.

The UK has already advised all British-flagged ships not to enter the Strait of Hormuz until the crisis is resolved. There are eight British-flagged ships in the region at present.

In his statement to MPs on Monday, Hunt vigorously defended the British decision to seize an Iranian tanker off Gibraltar on 4 July, insisting Britain – in cooperation with the US – had established that the ship entered British waters and was bound for Syria in breach of EU sanctions.

Iran says it is not party to EU sanctions on Syria, and points out that no ship previously heading for Syria has been impounded in this way. Iran claims the UK has in effect ended up supporting the US efforts to impose an Iranian oil export ban, a measure that the UK formally opposes as a supporter of the 2015 nuclear deal.

There is an urgency about the security of British ships, since one option is for British-flagged ships to be reflagged to avoid them becoming a target of the Iranians, something that would deal a blow to the British shipping industry. There are about 4,500 ships registered with Britain or its overseas territories.

Q&A Why is the Gulf of Oman so important for shipping oil? Show Hide The strait of Hormuz, which provides passage from the Gulf of Oman to the open sea, is the most important gateway for oil exports in the world. With Iran on its northern shore, and the UAE and Oman on its southern shore, the US Energy Information Administration (EIA) calls it the world’s worst 'chokepoint' In 2016, 18.5m barrels of crude oil were transported each day through the strait of Hormuz, compared with 16m through the strait of Malacca, which runs between the Indonesian island of Sumatra, Malaysia and Thailand, connecting the Indian Ocean with the South China Sea. 5m barrels of crude oil are transported annually through the next largest chokepoint, the Suez canal. Phillip Inman

Pompeo also dismissed Iran’s announcement that it had captured 17 spies working for the US Central Intelligence Agency and sentenced some to death.

Iran made the announcement in state media, saying the alleged spies had been arrested in the 12 months to March 2019. Such announcements are not unusual in Iran, but the timing has raised concerns that Tehran is hardening its position in its standoff with western powers. “The Iranian regime has a long history of lying ... I would take with a significant grain of salt any Iranian assertion about actions that they’ve taken,” Pompeo said.

Trump said on Monday that the Iranian claim was “totally a false story.”