Pence declares 'ISIS has been defeated' on the same day as deadly Syria attack

Pence's remark to the Global Chiefs of Mission conference at the US State Department came about an hour after the US-led coalition confirmed that American troops had been killed in an explosion in Manbij.

"U.S. service members were killed during an explosion while conducting a routine patrol in Syria today. We are still gathering information and will share additional details at a later time," the tweet from Operation Inherent Resolve said.

ISIS claimed responsibility for the attack, which the ISIS-affiliated Amaq agency said was carried out by a suicide bomber with an explosive vest.

Pence made no mention of the attack and did not offer condolences. His press secretary Alyssa Farah tweeted Wednesday morning that he had been briefed and that he and President Donald Trump were "monitoring the situation."

"Our hearts go out to the loved ones of the fallen," the tweet said. The coalition has not said how many service members were killed. Prior to Wednesday's attack, only two US service members had been killed in action in Syria since the start of the US campaign there in 2014.

The attack comes as the US prepares to withdraw troops from Syria -- a decision Pence defended in his Wednesday morning remarks.

"Thanks to the leadership of this commander in chief and the courage and sacrifice of our armed forces, we're now actually able to begin to hand off the fight against ISIS in Syria to our coalition partners and we're bringing our troops home," he said.

However, he said the US would "stay in the region and we'll stay in the fight to insure that ISIS does not rear its ugly head again."

"We will protect the gains that our soldiers and our coalition partners have secured," he said.