President Trump has urged China, Britain, France, Japan and South Korea to send warships to help reopen the waterway, even though they are not involved in the U.S.-Israeli attack on Iran.

President Trump’s call for some countries not involved in the U.S.-Israeli attack on Iran to send ships to help reopen the Strait of Hormuz has received cautious responses.

Mr. Trump named China, Britain, France, Japan and South Korea in a social media post on Saturday, urging them to join an effort to guard the waterway, a conduit for a fifth of the world’s oil shipments.

On Sunday, he warned that NATO faced a “very bad” future if members of the alliance did not help to open the Strait of Hormuz, adding that Europe was more reliant on Middle Eastern oil than the United States. “It’s only appropriate that people who are the beneficiaries of the Strait will help to make sure that nothing bad happens there,” he told the Financial Times.

Mr. Trump also threatened to delay a summit with China’s leader, Xi Jinping, which is expected to begin at the end of the month in Beijing.

Here is how nations have responded so far:

• Britain: Mr. Trump spoke with Prime Minister Keir Starmer on Sunday about the Strait of Hormuz and the disruption to global shipping, but no details were disclosed about whether Britain would contribute ships or other military assets. Earlier, Ed Miliband, the energy minister, said that Britain was looking at “any options” to help restart shipping in the region and was in talks with allies, without disclosing details. He reiterated Britain’s position that the “best and simplest way” for the strait to reopen was to de-escalate the fighting.

• Japan: Prime Minister Sanae Takaichi told Parliament on Monday that Japan had no plans to send warships to the Persian Gulf. “The Japanese government is currently considering how to take the necessary measures,” she said. Japan’s pacifist constitution limits military engagement in wars and a senior Japanese official had previously warned that any decision to deploy warships would face “high hurdles.” Takayuki Kobayashi, policy chief of the ruling Liberal Democratic Party, told the Japanese public broadcaster NHK on Sunday that the country would have to be cautious. The issue may come up during Ms. Takaichi’s planned meeting with Mr. Trump in Washington on Thursday.

• China: China, the biggest buyer of Iranian oil, has not responded directly to Mr. Trump’s remarks but has previously called for the cessation of hostilities. On Monday, Lin Jian, a spokesman for China’s foreign ministry, said the two sides were still discussing Mr. Trump’s planned visit to Beijing. The spokesman reiterated that China was committed to de-escalating the conflict.

• France: France has also not responded directly to Mr. Trump’s call publicly. President Emmanuel Macron has said that he would be willing to use the French navy to escort ships but only if the conflict stabilized. On Sunday, Mr. Macron wrote on social media that he had spoken with President Masoud Pezeshkian of Iran and told him that Tehran needed to ensure freedom of navigation through the Strait of Hormuz and reopen it to shipping.

• South Korea: The office of President Lee Jae Myung of South Korea said in a statement that it would “communicate closely with the United States,” but did not make any commitments.