In a post on Truth Social, Trump wrote on Saturday that countries affected by Iran's actions in the Strait of Hormuz will send warships there to, together with the United States, keep the strait "open and safe."
Trump listed China, France, Japan, South Korea and the United Kingdom as examples of countries that "hopefully" will contribute.
So far, reactions have been few. Takayuki Kobayashi, political director of Japan's ruling party, said on Sunday that the bar for sending warships to the Strait of Hormuz is "extremely high."
We do not rule out the possibility legally, but given the situation in which the conflict is taking place, this is something that must be treated with great caution, he told Japanese public service broadcaster NHK.
Similar voices are being heard from the UK.
The plan now must be to calm the conflict, the country's Energy Security Minister Ed Miliband told the BBC.
In South Korea, an official at the presidential office told AFP that the country is "closely following President Trump's statements on social media" and "will carefully consider the matter in close consultation with the United States."
Iranian Foreign Minister Abbas Araghchi is urging other countries not to do anything that risks escalating the war, he said in a phone call with French Foreign Minister Jean-Noel Barro on Sunday, according to a statement from Iran's Foreign Ministry.
Since the outbreak of war two weeks ago, Iran has attacked and threatened shipping traffic in the Strait of Hormuz - through which about a fifth of the world's oil passes.
