After days of deliberation and long before his self-imposed two-week deadline, Trump's decision to join Israel's military campaign against its primary rival, Iran, represents a significant escalation of the conflict and risks opening a new era of instability in the Middle East.

"The strikes were a spectacular military success," Trump said in a televised address.

"Iran's key nuclear enrichment facilities have been completely and totally obliterated."

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

The US reached out to Iran diplomatically on Saturday to say the strikes were all the US planned and it did 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."

An Iranian official, cited by Tasnim news agency, confirmed part of the Fordow site was attacked by "enemy air strikes".

However, Mohammad Manan Raisi, a lawmaker for Qom, near Fordow, told the Fars news agency the facility was not seriously damaged.

Iranian media quoted Iran's nuclear body as saying there were no signs of contamination after the attacks and no danger to residents living nearby.

Israeli Prime Minister Benjamin Netanyahu congratulated Trump on his "bold decision".

"History will record that President Trump acted to deny the world's most dangerous regime, the world's most dangerous weapons," Netanyahu said.

The strikes came as Israel and Iran have been engaged in more than a week of aerial combat that has resulted in deaths and injuries in both countries.

With AAP.