US President Donald Trump has not committed himself to joining Israel in the war against Iran, but he is moving military assets to within striking range of Tehran to keep that option open.

As part of the talks, Trump reportedly gave Tehran 60 days on March 19 to close a deal, a deadline that expired just before Israel launched a surprise attack on Iran early in the morning of June 13. As part of the negotiations Trump threatened to use military force if the talks were not successful and has been preparing the military option for months.

“There are two ways Iran can be handled: militarily, or you make a deal. I would prefer to make a deal, because I’m not looking to hurt Iran,” Trump told Fox News in March.

The US deployed six B-2 stealth bombers – one third of its B-2 force that cost $2bn each – at the start of April that can carry large 30,000lb bunker-busting GBU-57 Massive Ordnance Penetrator (MOP) bombs, a C-17 military transport aircraft and several refuelling tankers to the Indian Ocean island of Diego Garcia to “maintain operational readiness and ensure protection of strategic assets.” The Center for Strategic and International Studies noted the US has 19 B-2 bombers and approximately 20 GBU-57 bombs in total.

American warships have been shooting down Iranian ballistic missiles targeting Israel since the attack started. The USS The Sullivans in the Mediterranean and the USS Arleigh Burke in the Indian Ocean launched strikes over the weekend. The USS Thomas Hudner has joined The Sullivans in the Mediterranean to continue defence strikes in support of Israel, whereas the Arleigh Burke has reportedly been redeployed.

The USS Carl Vinson aircraft carrier is in the Arabian Sea with the four warships in its strike group. They are not participating in the defence of Israel. But they are positioned to provide security for US troops and bases along the Gulf of Oman and the Persian Gulf, AP reports.

The US sent two dozen refuelling aircraft from bases in the US to Europe on June 15, claiming the redeployment was a “pre-planned deployment.” AirNav systems, a flight tracking website, said more than 31 US Air Force refueling aircraft - primarily KC-135s and KC-46s - left the United States at the weekend. The planes landed at the Ramstein air base in Germany and airports in the United Kingdom, Estonia, and Greece.

The US relocated a dozen F-16s from a base in Italy to Prince Sultan, in Saudi Arabia, on June 17, according to Aurora Intel, AP reports.

On June 18 the USS Nimitz aircraft carrier was abruptly redeployed from the South China Sea towards the Middle East, the Financial Times reported on June 18 and will arrive in about a week. The Nimitz can hold 5,000 personnel and more than 60 aircraft, including fighter jets.

US Defence Secretary Pete Hegseth said in a post on X late on June 16 he had ordered the deployment of additional defensive capabilities to the Middle East, but did not offer specifics.

The United States already has a sizable force in the Middle East, with around 40,000 troops in the region, including air defence systems, fighter aircraft and warships that can help bring down missiles.

The US has dozens of installations in the region ranging from large bases to smaller outposts and access agreements. While exact numbers can vary due to operational secrecy and shifting deployments, the core network includes at least ten major bases in seven countries, supported by additional facilities and rotating forces.

The main bases include: Naval Support Activity Bahrain, home to the US Navy’s Fifth Fleet; Al Udeid Air Base in Qatar, the largest US military installation in the region and headquarters for US Central Command (CENTCOM)’s forward operations; Camp Arifjan and Ali Al Salem Air Base in Kuwait; Al Dhafra Air Base in the United Arab Emirates; Prince Sultan Air Base in Saudi Arabia; Ain al-Asad Air Base and Erbil Air Base in Iraq; and a network of undisclosed forward operating bases in northeastern Syria used primarily for counterterrorism missions.

In addition to its core installations, the US also operates smaller or more limited-access facilities in several countries. These include training and logistics sites in Jordan, airfield and port access agreements in Oman, and Incirlik Air Base in Turkey, which, while technically outside the Middle East, supports regional operations. In Israel, the US maintains a small but permanent presence, including a missile defence radar station, though it does not operate a formal base.

Diego Garcia will be the main forward operations base for long-distance bombing sorties targeting Iran’s hard-to-reach Fordow Fuel Enrichment Plant (FFEP), Iran’s primary facility for enriching weapons-grade uranium. Fordow is believed to be up to 90 meters deep inside a mountain near the city of Qom in Northern Iran.

Dropped from a B2 stealth bomber, the 6m-long MOP can reportedly penetrate with sheer kinetic force more than 60 metres of rock and soil — depending on the earth’s hardness — before exploding. Because it is precision-guided, multiple bombs can in theory be dropped on a single spot, the FT reports. 

According to a report from Axios, US President Trump is said to have doubts about whether the US Air Force’s GBU-57A/B MOP (Massive Ordnance Penetrator) would actually be able to reach and destroy FFEP.

Trump is said to have specifically asked his military advisers over the last few days about whether the 30,000lb “bunker buster” would be capable of destroying the Fordow Nuclear Facility, with defence officials telling the President they are confident it would, the FT reports. The MOP is more powerful than any known conventional bomb  and could in theory destroy much of Iran’s underground enrichment facilities, especially the Natanz site, which is thought to be buried 20m underground and encased in some 2m of reinforced concrete. 

However, it may not be enough to destroy the more-heavily protected Fordow facility, which is under as much as 80m of rock and soil. Rafael Grossi, head of the International Atomic Energy Agency, has said that some of Fordow’s most sensitive facilities may be buried even deeper.

One MOP bomb could be enough to destroy FFEP, but experts expect the US will use two or three in the event that the US joins the fray and may support that attack with a US or Israel mopping up ground operation by special forces.

If the US enters a direct war with Iran, it is possible that it will quickly expand its operations to strike Houthi targets in Yemen that have been plaguing the Red Sea transit of oil tankers via the Suez Canal. So far, the US airstrikes in Yemen are coordinated from two aircraft carriers deployed to the region — the USS Harry S. Truman in the Red Sea and the USS Carl Vinson in the Arabian Sea.

The UK has also promised to support the US militarily should America join the war against Iran, promising to provide refuelling planes some of which are also based in Diego Garcia at the jointly managed base.

Israeli officials believe that the US will eventually join the war and assist with the destruction of the Fordow Facility, but contend they could cause significant damage to the underground complex even if forced to go it alone, according to the FT. One option could be a commando raid against the Fordow by Israeli special forces, similar to the operation seen last September where Israeli forces raided and destroyed an underground missile factory to the north of the Syrian capital of Damascus. A US official said the Israelis told the Trump administration that while they may not be able to reach deep enough into the mountain with bombs, they may “do it with humans.”

The Nimitz carrier strike group — which includes three guided-missile destroyers — is expected to arrive in about a week. It will join another carrier group and multiple US destroyers already in the region, as pressure mounts to completely destroy Iran’s nuclear enrichment facilities.

Despite Israel’s intensified bombing campaign in recent days, analysts note that Israeli forces lack the capability to completely destroy Fordow on its own, which is buried deep beneath a mountain near the city of Qom. Experts estimated that four or five B-2 would be more than sufficient to conduct the mission with backup.

Trump said on June 18 that action “may be imminent,” and “the next week is going to be very big”, even before the Nimitz reaches its position.