US forces threatened with expulsion as tensions grow after Soleimani killing

The British government has asked Iraq to allow its troops to stay in the country, after the United States' killing of one of the most high-ranking military officials in neighboring Iran caused a huge rise in regional tensions.

There are currently around 400 British troops in Iraq as part of the US-led mission to fight Islamic State forces.

Iraq's Parliament voted to expel all 5,000 US troops following last week's killing of Iran's Major General Qassem Soleimani, prompting US President Donald Trump to threaten sanctions, a move Britain has no plans to follow.

The killing of Soleimani drew a vow of "severe revenge" from Iran's leadership. Trump replied by saying he has a list of 52 potential targets for future attacks, many of them cultural sites with no military connection. The number was chosen to signify the US hostages held by Iran in a yearlong hostage crisis in the late 1970s.

Iran also plans to abandon its commitments under the 2015 international nuclear deal, which had included limitations on its technical development, a deal from which the US has already withdrawn but which is still supported by other countries.

"Iran's announcement is clearly extremely concerning. It is in everyone's interests that the deal remains in place," said a spokesman for British Prime Minister Boris Johnson.

"It makes the world safer by taking the prospect of a nuclear-armed Iran firmly off the table. We have always said the nuclear deal is a reciprocal deal, and in light of Iran's announcement we are urgently speaking to partners about next steps."

Having returned from holiday to deal with the crisis after criticism he had not done so earlier, Johnson distanced himself from Trump's threats, which some observers have said would constitute a war crime because of the lack of military justification.

"There are international conventions in place which prevent the destruction of cultural heritage," said Johnson's spokesman.

Concerns for staff safety have seen staffing at the British embassies in Iran and Iraq reduced, although ambassadors, Rob Macaire in Iran and Stephen Hickey in Iraq will remain.

"The safety and security of our staff is of paramount importance and we keep our security posture under regular review. Both our embassies in Baghdad and Tehran remain open," said a Foreign Office spokesperson.

Foreign Secretary Dominic Raab said the safety of any affected British nationals was the government's main concern.

"Our first priority is to make sure that UK nationals, citizens, shipping, diplomatic missions and military personnel are safe," he said.

"We've changed our travel advice, we are going to be reinforcing in due course the Royal Navy protection for shipping in the Strait of Hormuz.

"On a diplomatic front our overwhelming message that the prime minister and I are conveying to our European and American counterparts, and also critically our partners in the Middle East, is the importance of deescalating the tensions and finding a diplomatic way through this crisis."