President Joe Biden said Sunday that the U.S. “shall respond” after three American troops were killed and dozens more were injured in an overnight drone strike in northeast Jordan near the Syrian border. Biden blamed Iran-backed militias for the first U.S. fatalities after months of strikes by such groups against American forces across the Middle East since the start of the Israel-Hamas war.

Biden, who was traveling in South Carolina, asked for a moment of silence during an appearance at a Baptist church’s banquet hall.