Secretary of State Antony J. Blinken will travel to Mexico City on Wednesday to discuss a surge in illegal immigration as thousands of migrants trek through southern Mexico in a mass movement toward the United States.

Mr. Blinken will meet with President Andrés Manuel López Obrador at a time when border crossings have hit record numbers. There have been days this month when the Border Patrol encountered more than 10,000 people at the southern border.

Wednesday’s meeting will also include Alejandro N. Mayorkas, the homeland security secretary, and Liz Sherwood-Randall, the White House homeland security adviser.

A huge caravan that began its journey north on Sunday is a sign of the enormous challenges in stemming the tide of migration. Local officials and news media reports in Mexico estimate that somewhere between 6,000 and 10,000 people are making the trip.

The southern border has been a consistent political vulnerability for President Biden, who promised on his first day in office to “restore humanity and American values to our immigration system” after the broad restrictions of the Trump years.

But Mr. Biden has struggled to keep the numbers down, despite trying to institute limits on asylum access at the border and deporting migrants to Venezuela and Cuba.