The administration of U.S. President Joe Biden vowed more strikes against Iran’s forces and its proxies in the Middle East after three straight days of punishing attacks, even as senior officials insisted the U.S. won’t be pulled into a prolonged regional conflict.

"We will respond forcefully, and we will respond in a sustained way,” White House National Security Advisor Jake Sullivan said on CBS’s Face the Nation. Even so, he said, Biden doesn’t see the U.S. action in the last three days as "some open-ended military campaign.”

Balancing between those two extremes will be Biden’s main challenge as he plots his next moves and braces for any counterattacks by Iran and its proxies. Officials framed the U.S. strikes — which hit 85 targets in Iraq and Syria on Friday, including some by long-range bombers flown from the U.S. — as a necessary and inevitable response to the killing of three U.S. soldiers in a drone strike in Jordan a week ago. "Yes,” Biden said when asked Sunday in Las Vegas whether the U.S. attacks are working.