Tijuana’s mayor, Juan Manuel Gastélum, has estimated that if all of the Central American migrants traveling north come to the city and seek asylum in the United States, it could take six months for their claims to be heard at the main port of entry to San Diego.

They must take their turn behind about 3,000 others — from Mexico, nations across Central and South America, and even West Africa — who are waiting for an interview with a United States asylum officer. The delay may last as long as two months.

New rules issued by the Trump administration this month are designed to funnel asylum seekers to an official port of entry rather than allowing them to present themselves to the Border Patrol if they make it across the border illegally.

As the bottleneck in Tijuana has grown, it has threatened to try the patience of a city that is itself the creation of migrants and typically provides for them through church-run shelters.