Trump says US Navy attacked and seized Iranian-flagged cargo ship

British Prime Minister Keir Starmer said in a statement on Monday that the U.K. will not take part in President Donald Trump's planned blockade of Iranian ports in the Strait of Hormuz, which is due to begin on Monday.

"We're not supporting the blockade," Starmer told BBC radio in an interview Monday morning, while declining to say whether the U.K. was sending minesweeper vessels to the Strait, as Trump indicated in an interview with Fox News.

"We do have mine-sweeping capability, I won't go into operational matters, but we do have that capability -- that's all focused, from our point of view, on getting the Strait fully open," Starmer said.

He reiterated his position that the U.K. will not join the conflict. "The UK is not getting dragged in," Starmer said. "That's not in our national interest, because I'm not going to act unless there's a clear, lawful basis and a clear thought-through plan."

French President Emmanuel Macron said in a Monday post to X that the U.K. and France are coordinating on a "peaceful multinational mission" to keep the Strait of Hormuz open to maritime traffic "as soon as circumstances permit."

The two countries will host a conference "in the coming days" Macron said.

"This strictly defensive mission, separate from the warring parties to the conflict, is intended to be deployed as soon as circumstances permit," Macron wrote. "No effort must be spared to swiftly reach, through diplomatic means, a strong and lasting settlement to the conflict in the Middle East."

-ABC News' Zoe Magee

The price of oil again climbed on Monday, after the United States said it would begin a blockade of the Strait of Hormuz.

The blockade -- which was expected to begin at 10 a.m. ET, according to U.S. Central Command -- appeared poised to continue the disruption of the vital maritime passageway off the southern Iranian coast, through which some 20% of the world’s oil supply is shipped.

Brent crude oil prices, a benchmark for global trading, climbed about 8% by 5 a.m. ET on Monday. It traded at more than $102 a barrel for deliveries in June.

U.S. crude prices for May contracts also advanced about 8% in early trading, climbing to about $103 per barrel.

Chinese Foreign Ministry spokesperson Guo Jiakun told reporters on Monday that Beijing hopes all warring parties "maintain calm and restraint" following the apparent collapse of U.S.-Iran peace talks over the weekend.

"China hopes that the relevant parties will strictly observe the temporary ceasefire arrangements, adhere to resolving disputes through political and diplomatic channels, avoid a resumption of hostilities and create conditions for the early restoration of peace and tranquility in the Gulf region," Guo said.

"The root cause of any disruption to navigation in the Strait lies in the conflict involving Iran, Guo said. "The way to resolve this issue is to achieve a ceasefire as soon as possible; all parties involved must maintain calm and restraint. China stands ready to continue playing a positive and constructive role."

Asked about reports that China is allowing Chinese weapons firms to send arms to Iran, Guo replied, "China has consistently adopted a prudent and responsible attitude toward arms exports, implementing strict controls in accordance with its domestic export control laws and regulations, as well as its international obligations. We oppose baseless smears and malicious insinuations."

-ABC News' Karson Yiu

The spokesperson for Iran's joint military command at Khatam al-Anbiya Central Headquarters said Monday that if the security of Iranian ports in the Persian Gulf and the Sea of Oman is threatened, "no port in the Persian Gulf and the Sea of Oman will be safe."

"Enemy-affiliated" vessels will not have the right to pass through the Strait of Hormuz, while other vessels will continue to be allowed transit "in accordance with the regulations of the Islamic Republic of Iran's armed forces," the spokesperson said, as quoted by Iran's state television Telegram channel.

"Given the continued threats," he said, the Islamic Republic will also implement "a permanent mechanism" to control the Strait of Hormuz, even after the war.

-ABC News' Somayeh Malekian