Ed Miliband is expected to meet with US secretary of state Marco Rubio a day after it emerged that the Trump administration was furious at his appointment as Foreign Secretary by Andy Burnham.
Mr Miliband in the Philippine capital Manila at the same time as Mr Rubio, with both attending the Association of Southeast Asian Nations (Asean) foreign ministers’ summit.
The event marks Mr Miliband’s international stage debut after his promotion by new prime minister Mr Burnham, who assembled his cabinet on Monday.
The White House is said to be “deeply concerned” about Mr Miliband’s appointment as foreign secretary, with a warning that Donald Trump has not forgotten scathing remarks the former Labour leader has made about him in the past.
The former energy secretary has previously clashed with the US president over net zero and his attitudes to democracy and in 2016 he described the president as “a racist, misogynistic, self-confessed groper”.
At the Asean summit, Mr Miliband called for calm in the conflict between Iran and the US, as Mr Trump threatened to “bomb and destroy” bridges and power stations.
He told foreign ministers gathered in the Philippines that the UK would “work intensively with others to seek to de-escalate this conflict”.
But Mr Trump, writing on his Truth Social platform, vowed to retaliate “any time the Islamic Republic of Iran shoots at a ship in the Strait of Hormuz”.
Speaking on Wednesday, Mr Miliband told ministers from Asean member states: “I know in particular how much the Iran conflict is affecting Asean partners.
“You are feeling as much as anyone across the world the daily impact on your economies and the living standards of your citizens, as well indeed as the impact on seafarers from many Asean nations.
“We too in the UK, in our own way, are feeling the effects of the conflict on families and businesses in the impacts on the cost of living.”
The Foreign Secretary added London “will work intensively with others to seek to de-escalate this conflict and find a diplomatic way forward”.
Any solution “must include reopening the Strait of Hormuz and upholding the fundamental principle of freedom of navigation”, he said.
Mr Miliband also said he welcomed a memorandum of understanding signed in June between the US and Iran, which included a deal for toll-free passage through the Strait of Hormuz for 60 days.
But efforts to honour the deal stalled when Iran targeted tankers in the Strait of Hormuz earlier this month.
At the time, Mr Trump took to Truth Social to declare that “the Cease Fire is OVER!”
The US president took to the platform again on Wednesday, when he wrote: “From this point forward, any time the Islamic Republic of Iran shoots at a ship in the Strait of Hormuz, whether it be by Missile, Rocket, Drone, or any other device or weapon, the United States will bomb and destroy ONE BRIDGE OR POWER PLANT, including those located next to, or in, the Capital City of Tehran.”
The warning came after the US carried out another wave of strikes on Iran, where air defences opened fire over Tehran.
Iran launched a missile attack on Aqaba, Jordan, and alerts were issued in Bahrain and Saudi Arabia.
Jordan’s military said it intercepted four Iranian missiles over Aqaba, while two others fell in “uninhabited areas”.
Mr Miliband was named Foreign Secretary on Monday, shortly after Andy Burnham entered No 10 for the first time.
The new Prime Minister has already spoken to the American leader, and his spokesman said their call was “extremely warm”.
A Downing Street spokesperson said the leaders discussed Mr Burnham’s “commitment to defence and security”, and the UK’s “commitment to securing the movement of shipping in the Strait of Hormuz to support global supply chains and drive down costs for businesses and families across the country”.
After the call, Mr Trump said the Prime Minister “has got a big job ahead of him, but he will be able to do it” and pledged that the US “will be there to help”.
The Republican president had previously described Mr Burnham as “extremely liberal” and “mayor of a town”.
Mr Burnham will continue letting the US use UK bases for defensive strikes against Iran as hostilities between the two sides ramp up again.
