WASHINGTON: US President Donald Trump on Monday (Jul 20) said Iran would "pay" for killing US soldiers after multiple service members were killed over the weekend as part of the United States' war against Iran, marking one of the deadliest days for US forces since the war started in February.

The number of US troops killed in the war on Iran rose to 17 over the weekend, with the remains of an additional service member being examined. Two of the personnel were confirmed to have been killed when Iran attacked US personnel in Jordan.

"Every time Iran kills an American Soldier they will pay for that killing many times over," Trump wrote on Truth Social. "This directive has been passed on to Secretary of War, Pete Hegseth, Chairman of the Joint Chiefs of Staff, Daniel Caine."

In March, six US troops were killed when an Iranian drone slammed into a US military facility in Port ​Shuaiba, Kuwait.

Roughly 430 US troops have been injured in the conflict so far.

The White House said Trump would attend the dignified transfer at Dover Air Force Base in Delaware for the service members killed.

It is unclear what specific "directive" Trump passed to the Pentagon. But a US official told Reuters that prior to the deadly attack in Jordan, the United States had already started moving additional military aircraft, including fighter jets and refueling tankers, to the Middle East.