As the war approaches the three-week mark, President Trump faces a battery of military and diplomatic choices that test his abilities as a leader.

The U.S. is pouring military resources into the region to combat the problem, and is launching a wave of strikes against Iranian forces and installations in hopes of reopening the strait — a key target for ending the war and relieving economic and political pressure on the White House.

The president has also urged allies to send warships to protect oil tankers in the strait. But he has engendered little goodwill with these countries, having repeatedly punished them with tariffs, insults and threats.

On Friday, Mr Trump said he would leave the task of reopening the strait to the countries that use it, claiming the US had not done so. “If asked, we will assist these countries in their Hormuz efforts, but this should not be necessary once the Iranian threat is eliminated,” he wrote on social media.

It was one of the mixed messages the Trump administration has sent about the war.

The options being considered to try to reopen the Strait of Hormuz are all complex and carry significant risks. None of these will guarantee immediate resolution of disputes.

Eliminate threats to shipping from land attacks.

U.S. commanders want to destroy as many of Iran’s missiles and drones as possible before the Navy can take merchant ships through the strait.

What it will take: In recent days, US warplanes have stepped up strikes in southern Iran against missiles and their launchers that can target slow-moving oil tankers and large cargo ships.

Earlier this week, the Army’s Central Command said Air Force F-15E fighter-bombers dropped several 5,000-pound bombs to penetrate layers of rock and concrete to destroy underground bunkers that store cruise missiles and support equipment.

The chairman of the Joint Chiefs of Staff, General Dan Cain, said that Iran’s missile-launching capability had declined by 90 percent since the start of the war. But he acknowledged that Iranian forces still have some firepower left.

General Kane added that some regional allies, whom he did not identify, were using Apache helicopter gunships “to handle one-way attack drones” that Iran has used to threaten shipping as well as its energy facilities in neighboring Arab countries and the Persian Gulf.

Sweep the strait for mines

US officials disagree on whether Iran has begun mining the strait. Intelligence officials say yes, while Pentagon officials say they haven’t seen clear evidence.

What it will take: Clearing the narrow waterway of Iranian mines would be a week-long operation, according to a former naval officer who was stationed on minefields in the Persian Gulf. And it could put American sailors in direct harm’s way.

Iran is believed to maintain a variety of naval mines. These involve small limpet mines containing only a few pounds of explosives that are placed directly on the hull by divers and usually detonate after a set time. Iran also has large diversionary mines that float just below the water’s surface, releasing 100 pounds or more of explosives when they come into contact with an unsuspecting vessel.

More advanced “bottom” mines sit on the sea floor. They use a combination of sensors — magnetic, acoustic, pressure and seismic — to determine when a ship is close, and explode with hundreds of pounds of force.

“It only takes one of those things to shut down traffic,” said Rear Adm. John F. Kirby, a retired naval officer. “Fear alone can paralyze the shipping industry, as we have already seen.”

The Navy had four minesweepers in the Gulf, each manned by 100 sailors, based in Bahrain. But those ships are now gone, one official said, replaced by three coastal warships that can sweep for mines but are also used for other purposes. And two ships, the USS Tulsa and the USS Santa Barbara, were spotted this week far from the Middle East, between Malaysia and Singapore, according to the military website The War Zone.

Follow Iran’s navy and fleet of fast boats.

The Pentagon has targeted the Iranian navy since the early hours of the war, destroying or damaging more than 120 ships, including several submarines. Its purpose was to eliminate Iran’s ability to block the strait and threaten neighboring countries.

But Iran’s Islamic Revolutionary Guard Corps also has hundreds of speedboats. A fighter armed with a rocket-propelled grenade on one of these boats could slip past American defenses and deliver a fatal blow to a tanker or warship.

What it will take: General Kane said low-flying Air Force A-10 Warthog aircraft are “hunting and killing fast attack watercraft” in competitive sea lanes. He said the A-10 was developed to provide close air support to US ground forces, but has been re-engineered to attack ships at sea.

U.S. warplanes are also targeting speedboats hidden in coastal areas, but Iran has stationed some of them in civilian ports, increasing the risks to civilians from any U.S. attack.

The US military is also attacking naval drone storage areas before the drones are launched.

Attack Kharg Island.

Admiral Brad Cooper, head of the military’s Central Command, said the US strike on Iranian military bases on the country’s oil-exporting Kharg Island had destroyed more than 90 targets, including naval mines and missile bunkers.

That has softened the island’s defenses if Mr. Trump follows through on his threat to seize the island and choke Iran’s oil economy, a possibility the Pentagon has played up in war-planning scenarios for years.

But Iranian troops are still on the island and US commanders say such a mission would be dangerous.

What it will take: About 2,200 Marines on three warships – equipped with drones, attack helicopters and fighter jets – have shortened patrols in the Indo-Pacific region, and are expected to arrive in the Persian Gulf region late next week. Marines are trained to conduct amphibious landings.

The U.S. military is sending 2,500 additional Marines to the Middle East next month, officials said Friday. They are expected to replace or augment those now in the area.

Another option involves paratroopers from special operations forces and elite units, such as the Army’s 82nd Airborne Division, taking the island. Once under control, the Americans would likely be attacked by any remaining Iranian forces on land or at sea.

On Thursday, the president said that before qualifying, he had no plans to send ground forces into combat: “I certainly wouldn’t tell you if I did.” He added that he would “do whatever it takes” to keep oil prices down.

Use naval escorts to escort oil tankers.

Mr Trump said on Friday that moving oil tankers through the Strait of Hormuz was “a simple military ploy”. Marine experts say it’s anything but.

Indeed, of all Mr. Trump’s options for opening the strait, naval escorts are perhaps the most difficult.

What it will take: Naval escorts are cumbersome operations requiring not only naval destroyers and littoral combat ships, but also attack aircraft.

Navy officials said the navy has deployed about 12 destroyers and warships in the area and could certainly send more, though that could take weeks. A Navy destroyer, equipped with an Aegis combat system that uses computers and radar to track and target, can protect oil tankers by firing cruise and ballistic missiles at land targets in Iran, while standard anti-missile systems can intercept incoming threats.

But a Navy official said that would require a higher ratio of naval destroyers than merchant ships, and would likely put a huge strain on naval assets. The Pentagon has already requested $200 billion in additional funding for the war.

Mark Montgomery, a retired rear admiral, estimated that about a dozen Navy destroyers, armed with helicopters and other aircraft, would be needed to ferry five or six tankers or cargo ships through the strait at a time — a transit that could take about 10 to 12 hours.

During the so-called tanker war between Iran and Iraq in the 1980s, the United States reflagged Kuwaiti tankers through the Persian Gulf and the Strait of Hormuz, part of Operation Ernst Will. USS Samuel B. Roberts was nearly destroyed by a mine, and USS Stark was heavily damaged by Iraqi missiles. In the end, 37 American sailors were killed.