Addressing a press conference at 10 Downing Street, the prime minister said that the Strait of Hormuz must be reopened to "ensure stability in the markets", but added that it is not a "simple task".
He said the UK is working with "all of our allies" to bring a "viable, collective plan" to restore freedom of navigation to the region.
Starmer asserted that he would not allow the UK to be drawn into a "wider war".

"I want to see an end to this war as quickly as possible. Because the longer it goes on, the more dangerous the situation becomes," he said.
Starmer also said that he spoke to US President Donald Trump on the phone on Sunday, during which the two discussed a number of issues.
Asked about his relationship with Trump, Starmer said, "It's a good relationship", and they had a "good discussion about the Strait of Hormuz".
"We are strong allies, have been for decades. But it is for me to act in what I consider to be in the best interest of Britain."

In a statement last night, a spokesperson for the British prime minister said that Starmer and Trump "discussed the ongoing situation in the Middle East and the importance of reopening the Strait of Hormuz to end the disruption to global shipping, which is driving up costs worldwide."
"The prime minister also expressed condolences for the American Service personnel who have lost their lives during the conflict. They agreed to keep in touch."