President Donald Trump tweeted Tuesday that Iran will pay a “very big price” after pro-Tehran forces attacked the U.S. embassy in Baghdad.

“The U.S. Embassy in Iraq is, & has been for hours, SAFE! Many of our great Warfighters, together with the most lethal military equipment in the world, was immediately rushed to the site. Thank you to the President & Prime Minister of Iraq for their rapid response upon request,” the president tweeted.

….Iran will be held fully responsible for lives lost, or damage incurred, at any of our facilities. They will pay a very BIG PRICE! This is not a Warning, it is a Threat. Happy New Year! — Donald J. Trump (@realDonaldTrump) December 31, 2019

“Iran will be held fully responsible for lives lost, or damage incurred, at any of our facilities. They will pay a very BIG PRICE! This is not a Warning, it is a Threat. Happy New Year!” he added.

The U.S. Embassy in Baghdad remained locked down Tuesday after hundreds of Iraqi protesters who attempted to storm the compound failed to gain entry, U.S. officials said.

An embassy spokesman told CNN the embassy personnel were secure following an assault by protesters who were angered by a series of deadly American airstrikes carried out Sunday against an Iranian-backed Iraqi militia group in Iraq and Syria.

Protesters entered the heavily fortified “Green Zone” near the compound after apparently being granted access by Iraqi security forces and gathered at the walls of the embassy itself to denounce the U.S. airstrikes against the Kata’ib Hezbollah militia.

U.S. officials blamed the militia for the death of a U.S. contractor in Kirkuk, Iraq, late last week.

Hours after the attack, President Trump accused Iran of orchestrating the event, vowing to “strongly responded.”

“Iran killed an American contractor, wounding many. We strongly responded, and always will. Now Iran is orchestrating an attack on the U.S. Embassy in Iraq. They will be held fully responsible. In addition, we expect Iraq to use its forces to protect the Embassy, and so notified!” the president wrote on Twitter.

Iran killed an American contractor, wounding many. We strongly responded, and always will. Now Iran is orchestrating an attack on the U.S. Embassy in Iraq. They will be held fully responsible. In addition, we expect Iraq to use its forces to protect the Embassy, and so notified! — Donald J. Trump (@realDonaldTrump) December 31, 2019

The UPI contributed to this report.