Mr Biden, who was travelling in South Carolina on Sunday, asked for a moment of silence during an appearance at a Baptist church’s banquet hall.
“We had a tough day last night in the Middle East, and we shall respond,” he said.
With an increasing the risk of military escalation in the region, US officials were working to identify the precise group responsible for the attack, but they have assessed that one of several Iranian-backed groups was behind it.
Mr Biden said in a written statement that the United States “will hold all those responsible to account at a time and in a manner (of) our choosing.”
