The US wants to step up international naval patrols to protect shipping in the Arabian Gulf after warships were forced to escort a UK-flagged tanker this week to counter the threat of an Iranian attack.
Washington wants allies over the coming weeks to send ships to the region to secure commercial shipping and prevent further attacks that could harm the world oil supply.
“We’re engaging now with a number of countries to see if we can put together a coalition that would ensure freedom of navigation both in the Straits of Hormuz and the Bab Al Mandeb,” said Gen Joseph Dunford, chairman of the US Joint Chiefs of Staff.
“Probably over the next couple of weeks we’ll identify which nations have the political will to support that initiative and then we’ll work directly with the militaries to identify the specific capabilities that will support that.”
The announcement came on the same day that US President Donald Trump tweeted that "sanctions will soon be increased, substantially," on Iran.
Mr Trump accused Iranian leaders of "secretly enriching'" in breach of the nuclear deal Tehran signed with world powers in 2015.
Vessel-tracking agencies showed at least two British warships shadowed the tanker, Pacific Voyager, through the Strait of Hormuz on Tuesday.
The military escort followed concerns of a response by Iran after the seizure by British marines last week of a vessel suspected of carrying Iranian crude to Syria.
Gen Dunford released details of the plan after meetings on Tuesday with acting US Defence Secretary Mark Esper and Secretary of State Mike Pompeo.
This week, a senior Emirati official told The National that the UAE supported a collective, co-ordinated response to protect shipping and counter threats in the Gulf.
The official did not refer to a specific plan, such as the one mentioned by Gen Dunford, but said there had been a lot of co-ordination with the US and other allies after the recent tanker attacks.
Just over a year ago, the US administration pulled out of the 2015 nuclear deal that set strict limits on uranium enrichment and use in exchange for sanctions relief.
The White House has placed strict sanctions on Iran since withdrawing from the deal.
Tension in the region escalated after four tankers were sabotaged with mines off the coast of Fujairah in May.
Less than a month later, two more tankers were attacked in the Gulf of Oman. The US has blamed Tehran for all attacks.
Iran-backed Houthi rebels in Yemen have also stepped up drone attacks on Saudi Arabia, a move the US has said was directed by Tehran.
Dozens of civilians have been wounded and at least one killed in Yemeni rebel drone attacks on Abha airport in southern Saudi Arabia.
Gen Dunford said the US would provide “command and control” ships but other countries should provide craft to patrol waters between the American naval vessels.
The third part of the mission would involve coalition members escorting their countries’ commercial vessels, he said.
Gen Dunford said the size of the campaign could be adjusted based on the number of countries that committed to it.
“So with a small number of contributors we can have a small mission," he said. "And we’ll expand that as the number of nations that are willing to participate identify themselves.”
Although oil markets have not reacted to the tension with any major price increases, about 21 million barrels a day pass through the Strait of Hormuz – the chokepoint between the Arabian Gulf and the Gulf of Oman.
That means as much as a fifth of the world’s oil supply could be affected if Iran closed the narrow channel, as it has threatened to do.
Iraqi Prime Minister Adel Abdul Mahdi said on Tuesday that any disruption to oil exports through the Strait of Hormuz would be a “major obstacle” for his country’s economy.
His government was studying contingency plans to deal with possible disruptions, including alternative routes for oil exports, Mr Abdul Mahdi said.
The US has repeatedly said that any attempt by Iran to close the Strait would result in a swift military response.
US officials said that part of the reaction to the May and June attacks involved co-ordinating closely with regional partners and allies to determine what steps to take next.
They had publicly discussed plans to protect the Strait of Hormuz, but Gen Dunford disclosed that the coalition would also seek to bolster security in the Bab Al Mendab off the west coast of Yemen.
While no ships in that crucial channel have been hit, Houthi rebels have attacked vessels there. Bab Al Mandeb is only 20 kilometres wide at its narrowest point,
Almost 4 million barrels of oil are shipped daily through the strait to Europe, the US and Asia, as well as commercial goods. The channel leads north to the Suez Canal.
This week, the Saudi-led coalition fighting in Yemen said it intercepted an unmanned, bomb-laden vessel used to strike commercial shipping near Bab Al Mandeb.
Last year, Saudi Arabia, the world’s biggest crude exporter, stopped shipments through the strait because of a Houthi attack on a tanker. Riyadh resumed them 10 days later.
Washington’s plan is largely in line with its often stated aim of protecting the free movement of shipping through international waters.
The US has sent military vessels and aircraft to conduct symbolic manoeuvres in contested or tense areas to demonstrate its commitment to free navigation.
But the American carrier group led by the USS Abraham Lincoln, which was sent to the Gulf to respond to Iranian threats, has stayed out of the Strait of Hormuz to avoid unnecessary escalation.
The group has remained hundreds of kilometres from the vital strait.
"You don't want to inadvertently escalate something," Capt Putnam Browne, the commanding officer of the Lincoln, said in June.
Iran has repeatedly threatened to hit US vessels.
“Our missiles will destroy their aircraft carriers if they make a mistake,” Hossein Nejat, a commander of the Islamic Revolutionary Guard Corps, said on Tuesday night.
Mr Nejat said the US was “well aware of the consequences of a military confrontation with Iran” and that American bases were within range of Iranian ballistic missiles.