TIJUANA, Mexico — The vanguard of what President Trump has labeled an invasion force formed an orderly line at about 6:45 a.m. on Thursday near a major border crossing between Tijuana and the United States and waited patiently.

About 80 lesbian, gay, bisexual and transgender people who have been traveling with a large migrant caravan had come to the crossing, with stories of victimization and persecution, to make appointments for asylum interviews in the United States.

But other than the line of migrants, it was mostly business as usual along this westernmost stretch of the Mexico-United States southwest border.

A steady flow of pedestrians and cars traversed the official border crossings, in an apparently smooth and normal process. Contractors worked on the steel border fence that reaches across the beach and into the Pacific Ocean, unfurling concertina wire along the top of the barrier and across the sand while American military police officers looked on.