The delays could remain a fact of life across the southern border for the next few years, border officials said, at least until new security technology and expanded entry stations are installed and until Americans get used to being checked and questioned like foreigners. Last year 234 million travelers entered the United States through land border crossings from Mexico.

W. Ralph Basham, the commissioner of Customs and Border Protection, the agency that manages the borders, said longer waits had resulted from added security measures at border stations that in many cases were aging, outmoded and facing surging traffic. Saying the new document checks were a “security imperative,” Mr. Basham called on border cities, which own many of the crossing bridges, to invest in expanding the entry points.

In the meantime, Mr. Basham said, “A safer border is well worth the wait.”

Wait times of up to three hours have also been reported over the past few months at crossings from eastern Canada. Senator Bernard Sanders, independent of Vermont, who held a series of town meetings with border officials about the lines, said low staffing at border stations was the primary cause there.

The longer lines along the Mexico border have been especially unsettling here in El Paso, a humming border city long comfortable in its marriage to Ciudad Juárez, the bigger and rowdier Mexican metropolis on the other bank of the Rio Grande. Lines of cars and pedestrians at sunrise on the four border bridges here are a routine for tens of thousands of people, including many United States citizens, coming from Mexico on their way to school, work and shopping.

“International bridge wait times continue to escalate, causing frustration and concern in my district and across the nation,” wrote El Paso’s congressman, Representative Silvestre Reyes, a Democrat, in a letter this month to the House Committee on Homeland Security in which he called for a hearing on the matter.