Trump says Iran will 'pay a very big price' if lives are lost at any U.S. facility

U.S. President Donald Trump said on Tuesday that Iran will be held accountable for lives lost in attacks on any U.S. facilities.

"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," Trump wrote on Twitter hours after protesters angry about U.S. airstrikes on Iraq hurled stones and torched a security post at 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," Trump said.