"We expect Iraq to use its forces to protect the Embassy, and so notified!" Trump tweeted.

Iraqi supporters of pro-Iran factions attacked the embassy early Tuesday, breaching its outer wall and chanting "Death to America" in anger over weekend air strikes that killed two dozen fighters.

It was the first time in years that protesters have been able to reach the US embassy, which is sheltered behind a series of checkpoints in the high-security Green Zone.

Trump blamed Iran for organizing the attack and warned Tehran would be held accountable.

"Now Iran is orchestrating an attack on the US Embassy in Iraq. They will be held fully responsible," he tweeted.

The demonstrators were protesting against US air strikes that killed at least 25 fighters from a hardline Hashed faction known as Kataeb Hezbollah (Hezbollah Brigades) on Sunday.

Those strikes were in response to a 36-rocket attack last week that killed one American contractor at an Iraqi base, the latest in a string of attacks on areas where US troops are deployed.

They have not been claimed, but US security assessments have largely blamed them on Kataeb Hezbollah.

In his tweet, Trump said the US had "strongly responded" to the attack that killed the US contractor and "always will" in similar situations.

Relations between Washington and Tehran have deteriorated since the US in 2018 pulled out of the landmark Iran nuclear deal.

Trump has since imposed sweeping sanctions aimed at curbing the clerical regime's regional influence.

Iraq had long feared being caught in the middle of escalating tensions between the two countries, which are its main allies.