The conflict in northeast Syria escalated Friday as Iran-backed militias launched a volley of rocket and drone attacks against coalition bases after American reprisals for a drone attack that killed a U.S. contractor and injured six other Americans.

President Joe Biden, speaking at a news conference in Canada, sought to tamp down fears that tit-for-tat strikes between the United States and militant groups could spiral out of control, while at the same time warning Iran to rein in its proxies.

"Make no mistake, the United States does not, does not, I emphasize, seek conflict with Iran,” Biden said in Ottawa, Ontario, where he was making a state visit. "But be prepared for us to act forcefully to protect our people. That’s exactly what happened last night.”