Trump: Iran will 'pay a very big price' if lives are lost at US 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. air strikes on Iraq hurled stones and torched a security post at the U.S. Embassy in Baghdad.