Earlier this week Trump urged countries including the UK to support efforts to reopen the oil shipping channel, the Strait of Hormuz.
The number of ships passing through the strait has plummeted since the conflict began, with Iran threatening to attack certain vessels with drones and missiles.
The blockage has caused a dramatic rise in the price of oil and gas prices, triggering turbulence in the financial markets.
Sir Keir has said he is working with allies on a “viable, collective plan” to reopen the strait.
He has warned that the longer the conflict continues, “the bigger the impact on the cost of living,” adding that “the best way forward is a negotiated settlement with Iran”.
The Green Party of England and Wales has urged the UK government to withdraw permission for the US to use its military bases for attacks on Iran and “refuse any further complicity in this illegal war”.
In a letter to the prime minister, Green Party MPs and peers ask the government to set out what action it was taking to ensure military bases were only being used for defensive purposes.
It also asked for an assessment of how many Iranian civilians had been killed by “US bombing missions from British air bases”.