Minister to call for 'urgent de-escalation' on Iran visit
Foreign Office minister Andrew Murrison will call for "urgent de-escalation" of regional tensions during talks with the Iranian government in Tehran on Sunday.
The US has accused Iran of attacking oil tankers, and President Trump warned Iran faces "obliteration" in a war.
On Thursday he called off airstrikes with 10 minutes to spare, after Iran shot down a US drone.
The Foreign Office said that Dr Murrison will criticise Iran's "regional conduct" on the short visit.
It added the UK still supported the Iranian nuclear deal - that Mr Trump ditched in 2018.
A spokeswoman said: "The UK has an ongoing diplomatic dialogue with Iran.
"At this time of increased regional tensions and at a crucial period for the future of the nuclear deal, this visit is an opportunity for further open, frank and constructive engagement with the government of Iran.
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"Dr Murrison will call for urgent de-escalation in the region and raise UK and international concerns about Iran's regional conduct and its threat to cease complying with the nuclear deal, to which the UK remains fully committed."
It comes as reports said the US launched a cyber-attack on Iranian weapons systems on Thursday.
According to the Washington Post, the attack disabled computer systems controlling rocket and missile launchers.
The New York Times said it was in retaliation for Iran's shooting down of the US drone and attacks on oil tankers that the US has blamed Iran for.
Former Labour Foreign Secretary David Miliband said the UK should be "very worried" about the "real prospect of a war".
Speaking on the BBC's Andrew Marr Show, he said such a conflict would become a "contagion across the region".
"There are people in the senior reaches in the US administration who want a war with Iran, and there are people on the Iranian side who are itching to get at the Americans too.
"A war between US and Iran would not be restricted to the US and Iran," he concluded.
Tensions have been escalating between the Iran and the US after Mr Trump unilaterally pulled out of a 2015 nuclear deal aimed at curbing Iran's nuclear activities.
Iran shot down the unmanned aircraft on Thursday morning. Washington and Tehran dispute whether it was in international airspace at the time.
The shooting down of the drone followed accusations by the US that Iran had attacked two oil tankers with mines last Thursday just outside the Strait of Hormuz, in the Gulf of Oman.
The president said he called off the air strikes after being told 150 Iranians would be killed.
Speaking to NBC on Friday, President Trump said the US was open to talks with Iran but would not allow it to develop nuclear weapons.
Iran recently announced it will soon exceed international agreed limits on its nuclear programme.
Also on Dr Murrison's agenda is likely to be the plight of British citizen Nazanin Zaghari-Ratcliffe, who was jailed by an Iranian court for five years in 2016 over a disputed spying conviction.
Her husband, Richard Ratcliffe, who is on day eight of a hunger strike outside the Iranian Embassy, said the foreign minister's visit was "really helpful".
"I'm not sure if I'm hopeful, but certainly will be watching very closely to see how things develop and what comes back," he added.
"The sooner the British government's able to work with the Iranian government and find a resolution, [the] better for our family."