Trump had spent weeks pursuing a diplomatic path to replace the nuclear deal with Tehran that he tore up in 2018.

But he has since backed Israel's military campaign against Iran's nuclear facilities and top military brass, which it launched a little over a week ago.

AFP examines what we know about the US strikes on Iran.

- The targets -

Trump said the United States struck three main Iranian nuclear sites: Fordo, Natanz and Isfahan, with the former being hit with a "full payload of bombs."

Fordo -- which was built in violation of UN resolutions under a mountain near the holy central city of Qom -- was an enrichment plant capable of housing about 3,000 centrifuges.

Centrifuges are used to enrich uranium, both for civilian and military use, with the radioactive metal needing to be enriched to high levels for use in atomic weapons.

Fordo's location deep underground presented a challenge to Israeli forces, which do not have the deeply penetrating munitions needed to hit the facility.

Natanz was Iran's main uranium enrichment site, with nearly 70 cascades of centrifuges at its two enrichment plants, while a uranium conversion facility and a nuclear fuel fabrication facility were located at Isfahan.

- The munitions -

Trump did not identify the type of munitions used in the strikes, but the GBU-57 -- a powerful 30,000-pound (13,600-kilogram) American bunker-busting bomb -- was likely used to hit Fordo.

The US military says the GBU-57 -- also known as the Massive Ordnance Penetrator -- is designed to penetrate up to 200 feet (60 meters) underground before exploding.

This differs from most other missiles or bombs that typically detonate their payload near or upon impact.

Testing of the weapons began in 2004 and Boeing was in 2009 awarded a contract to complete the integration of GBU-57 with aircraft.

- The aircraft -

The only aircraft capable of deploying the GBU-57 is the American B-2 Spirit, a long-range stealth bomber that can carry two.

Prior to the Iran strikes, specialist flight tracking sites and US media reported that multiple B-2s had left a base in Missouri in the central United States.

The bombers -- which can fly 6,000 nautical miles (9,600 kilometers) without refueling -- are designed to "penetrate an enemy's most sophisticated defenses and threaten its most valued, and heavily defended, targets," according to the US military.

The B-2 was first publicly displayed in 1988 and flew for the first time the following year, with the first of the planes delivered in 1993.

The bomber took part in operations against Serbian forces in the 1990s, flying non-stop from Missouri to Kosovo and back. B-2s were subsequently employed by the United States in the Afghanistan and Iraq wars in the 2000s.

- What comes next? -

Trump called on Iran to "agree to end this war," saying that "now is the time for peace."

But it remains to be seen whether the strikes will push Tehran to deescalate the conflict, or to widen it further.

If Iran chooses the latter option, it could do so by targeting American military personnel who are stationed around the Middle East, or seek to close the strategic Strait of Hormuz, which carries one-fifth of global oil output.