TIJUANA, Mexico (AP) — Just after people raised their glasses to ring in the New Year, about 150 migrants gathered at a section of border wall in Tijuana to try to cross into the United States, many of them asylum seekers fed up with the long wait to have their claims processed.

On the other side, U.S. Border Patrol agents wearing camouflage and night-vision goggles and carrying assault-style rifles yelled, "Don't jump. It's dangerous. Get back!" in Spanish. American activists accompanying the migrants shouted at agents in English not to fire tear gas because children were present.

Several mig...