WASHINGTON - US forces struck three Iranian nuclear sites in a "very successful attack," President Donald Trump said on Saturday, adding that Tehran's nuclear program had been obliterated.

After days of deliberation and long before his self-imposed two-week deadline, Trump's decision to join Israel's military campaign against its major rival Iran represents a major escalation of the conflict.

"The strikes were a spectacular military success," Trump said in a televised Oval Office address. "Iran's key nuclear enrichment facilities have been completely and totally obliterated."

In a speech that lasted just over three minutes, Trump said Iran's future held "either peace or tragedy," and that there were many other targets that could be hit by the US military.

"If peace does not come quickly, we will go after those other targets with precision, speed and skill."

The US reached out to Iran diplomatically on Saturday to say the strikes are all the US plans and it does not aim for regime change, CBS News reported.

Trump said US forces struck Iran's three principal nuclear sites: Natanz, Isfahan and Fordow. He told Fox News six bunker-buster bombs were dropped on Fordow, while 30 Tomahawk missiles were fired against other nuclear sites.

US B-2 bombers were involved in the strikes, a US official told Reuters, speaking on condition of anonymity.

"A full payload of BOMBS was dropped on the primary site, Fordow," Trump posted. "Fordow is gone."

"IRAN MUST NOW AGREE TO END THIS WAR," he added.

Reuters