"There are those who advocate for the liberation of the Strait of Hormuz by force through a military operation, a position sometimes expressed by the United States," Macron said during a visit to South Korea.

"I say sometimes because it has varied, it is never the option we have chosen and we consider it unrealistic," he said.

Macron said such an operation would take excessive time and expose those crossing the strait to "coastal threats", particularly from Iran's Revolutionary Guards "who possess significant resources as well as ballistic missiles".

"This can only be done in concert with Iran," the French leader added, calling first for a ceasefire and a return to negotiations.

The Strait of Hormuz, a vital shipping route for oil, has been virtually paralysed for weeks by the Middle East war, pushing up prices for crude and related products worldwide.

Iran's Revolutionary Guards have vowed to keep the strait shut to the country's "enemies" while Trump has made reopening it a condition for a ceasefire.

US President Trump in a prime-time White House address on Wednesday again said that countries that receive oil through the strait "must take care of that passage".

In earlier comments he singled out European and Asian countries.

"You know, we only have 45,000 soldiers in harm's way over there, right next to a nuclear force. Let South Korea do it," Trump said, referring to North Korea.

"Let Japan do it. They get 90 percent of their oil from the Strait. Let China do it. Let them all do it. What the hell are we doing it for?"

The United States has around 28,500 troops in South Korea.

Macron, who landed in South Korea on Thursday after visiting Japan, also expressed frustration at Trump's statements on the conflict.

"You have to be serious. When you want to be serious, you don't say the opposite every day of what you said the day before. And perhaps you shouldn't talk every day," Macron said.

The French president also said that Trump -- who on Wednesday poked fun at Macron's marriage and accent -- was undermining the NATO alliance.

"If you create daily doubt about your commitment, you hollow it out," Macron said, adding that there is "too much talk... going off in all directions".

The comments about his marriage were "neither elegant nor up to standard" and "do not merit a response."

- K-pop dinner -

Macron's two days in South Korea includes talks with President Lee Jae Myung, a visit to a war memorial to pay tribute to French soldiers who fought in the Korean War, as well as an economic forum and dinner with K-pop stars and filmmakers.

In Japan, Macron signed a roadmap on critical minerals and defence cooperation and met Prime Minister Sanae Takaichi as well as the emperor.

In an opinion piece in Le Figaro, Lee called for stronger cooperation with France, particularly in key areas such as artificial intelligence, nuclear energy, hydrogen technologies and space.

The war has already prompted South Korea to impose a fuel price cap to ease pressure on its energy supply, the first such measure since 1997, and put forward a special "wartime" extra budget.

"The current crisis is not like a passing shower that will stop, but rather like a massive storm that could last indefinitely," Lee told the National Assembly on Thursday.