Foreign Secretary Dominic Raab has urged Iran to “take a diplomatic route” to de-escalate tensions and come in “from the international cold”.
It comes amid heightened tensions in the Middle East following the US killing of Iran’s top military leader, Qasem Soleimani, in Iraq.
Mr Raab told the BBC the US “had a right to exercise self-defence”.
It comes as Royal Navy warships have been ordered to escort British-flagged vessels in the Persian Gulf.
There are fears Iran will seek revenge for the death of Soleimani, who was killed in a US drone strike in Baghdad, Iraq on Friday.
Meanwhile, Prime Minister Boris Johnson is due to return to the UK after a 12-day holiday and will talk to foreign leaders in the coming days.
The killing of Soleimani marks a major escalation in tensions between the US and Iran, with Tehran vowing to avenge his killing.
US President Donald Trump last night tweeted that the US will strike 52 Iranian sites “very fast and very hard” if Tehran follows through with its vow of revenge.
Speaking to the BBC’s Andrew Marr programme on Sunday, Mr Raab said: “The president of the US, the president of France have left the door open to a diplomatic route through this, to a better place for Iran. The leadership have decided not to take it.”
He added the “important thing now is to de-escalate the tensions and try and restore some stability” – while trying to contain Iran’s “nefarious actions”.
“Iran has for a long period been engaged in menacing, de-stabilising activities,” he said.
Mr Raab said he first became aware of the killing of Gen Soleimani “as it happened” and spoke to US counterpart Mike Pompeo – who he will meet in Washington this week – on Friday.
Pressed on whether it could have helped the UK to be warned about the airstrike in advance, Mr Raab said: “I’m not sure it would have made the kind of wholesale difference that you’re suggesting.”
Defence Secretary Ben Wallace said HMS Montrose and HMS Defender will accompany UK-flagged ships through the Strait of Hormuz, as they did between July and November following the seizure of a British-flagged tanker by Iran.
He said he had spoken to his US counterpart, Mark Esper, on Friday and urged all parties to de-escalate the situation.
But Mr Wallace added: “Under international law the United States is entitled to defend itself against those posing an imminent threat to its citizens.”
Mr Johnson is expected to return to the UK later after spending almost two weeks on the Caribbean island of Mustique.
He has yet to speak publicly about the US airstrike or subsequent threats from Iran.
Outgoing Labour leader Jeremy Corbyn renewed his criticism of the PM for not cutting short his holiday and called for an urgent meeting of the Privy Council – the group that advises the Queen – over the airstrike.
Mr Pompeo had criticised America’s European allies for not being “helpful” in the wake of the assassination. However, he later said in a tweet that he was “thankful that our allies recognise the continuing aggressive threats posed by the Iranian Quds Force”.
Mr Raab is expected to meet his French and German counterparts before travelling to the US capital on Thursday.
Following the strike, the Foreign Office has hardened its travel advice for Britons in Iraq and Iran. Officials also urged those travelling to the United Arab Emirates, Turkey and Israel to “remain vigilant”.
In its advice, published on Saturday, the Foreign Office said there is a risk that British or British-Iranian dual nationals “could be arbitrarily detained or arrested in Iran”.
“The criminal justice process followed in such cases falls below international standards,” it said.
The Foreign Office also said alerts for other parts of the Middle East were being increased, with calls for citizens to “remain vigilant” in nations including Afghanistan, Israel, Lebanon, Saudi Arabia and the United Arab Emirates.
It advised people to keep up to date with developments via the media and its own travel advice.
It comes as the US has pledged to send 3,000 extra troops as a precaution. The UK has 400 troops based in the Middle East and works alongside US forces in the region.
On Saturday, around 150 people gathered outside Downing Street for an “emergency” protest organised by the Stop the War Coalition, urging the US to avoid more conflict with Iran.