About a fifth of global oil and liquefied natural gas normally passes through the strait, a narrow passage of water between Iran and Oman.
Iran's ability to stop shipping through the channel could give it enormous leverage over the US and its allies.
"The Countries of the World that receive Oil through the Hormuz Strait must take care of that passage, and we will help - A LOT!" Trump wrote in a Truth Social post.
"The US will also coordinate with those Countries so that everything goes quickly, smoothly, and well."
In an earlier post on Saturday, Trump predicted that "Many Countries, especially those who are affected by Iran's attempted closure of the Hormuz Strait, will be sending War Ships, in conjunction with the United States of America, to keep the Strait open and safe."
Trump wrote that he hoped China, France, Japan, South Korea, the United Kingdom and others would send ships to the area.
"In the meantime, the United States will be bombing the hell out of the shoreline, and continually shooting Iranian Boats and Ships out of the water," he wrote.
The White House did not respond to a request for comment on whether any countries had agreed to send ships.
Traffic through the narrow waterway - vital for global oil exports - has nearly collapsed during the war with Iran, pushing prices higher.
Following consultations among the G7 countries, French President Emmanuel Macron said this week the group was preparing a naval mission to escort oil tankers and cargo ships through the strait.
While the initiative has been promoted by Macron, German Chancellor Friedrich Merz said he sees no need for an international military deployment.
The UK government is talking to allies and partners about "a range of options to ensure the security of shipping in the region," a Ministry of Defence spokesperson said on Saturday.
The French Navy is deploying about a dozen naval vessels, including its aircraft carrier strike group, to the Mediterranean, Red Sea and potentially the Strait of Hormuz as part of defensive support to allies threatened by the conflict.
As the war entered its third week on Saturday, Iran projected defiance after US forces hit military sites at its own main oil hub, warning that parts of the United Arab Emirates were a legitimate target and urging civilians to leave.
The war has killed more than 2000 people, mostly in Iran, and created the biggest oil supply disruption in history, pushing prices sharply higher as maritime traffic has halted in a region that delivers a fifth of the world's oil.
Some oil-loading operations have been suspended in the UAE's Fujairah emirate, a major bunkering hub and crude export terminal, industry and trade sources said on Saturday, with TV footage showing plumes of dark thick smoke rising into the air.
Trump had threatened to strike the oil infrastructure of the Kharg Island hub unless Iran stopped attacking vessels in the Strait of Hormuz.
Trump on Friday said the US had "totally obliterated" military targets on the island, the export terminal for 90 per cent of Iran's oil shipments, which lies about 500km northwest of the strait.
Iran, however, played down the extent of the damage while threatening to step up its use of more powerful weapons and warning parts of the UAE were a legitimate target.
Foreign Minister Abbas Araqchi said Iran would respond to any attack on its energy facilities and warned it would target US companies in the region or companies in which the US had shares.
The UAE's foreign ministry did not immediately respond to the Iranian accusation that the attack on Kharg Island came through the UAE.
Nine ballistic missiles and 33 drones were launched from Iran towards the UAE on Saturday, the UAE defece ministry said.
Iranian authorities warned residents to leave areas near Jebel Ali port in Dubai, Khalifa port in Abu Dhabi and the UAE's Fujairah port and said it was targeting branches of US banks in the Gulf.
Fujairah, outside the Strait of Hormuz, is the outlet for about a million barrels per day of the UAE's Murban crude oil - a volume equal to about 1 per cent of world demand.
with DPA
