A group of about 2,000 migrants left Mexico's southern border Sunday hoping to reach the country's north and ultimately the United States. The development comes weeks before the U.S. presidential election, in which immigration has been a key issue.

Some migrants, like Venezuelan Joel Zambrano, believe a new administration in the U.S. could put an end to asylum appointments through an online system called CBP One.

“That is what makes us fearful. They say this could change because they could both close the CBP One appointment and all the services that are helping migrants," he said.

Both the lack of jobs in Mexico's south due to a new wave of incoming foreigners and a delay in asylum appointments in the U.S. have motivated more groups of migrants to leave the region in the past month.

“The situation in my country is very bad, the president doesn't do anything for us. We spent a week by the border, but getting documents takes time," said Honduran Roberto Domínguez, 48. “The documents we get are only for us to be in Tapachula and we cannot leave the city.”

The group leaving Sunday was the third and the largest since the beginning of the administration of new Mexican President Claudia Sheinbaum, who so far has made no changes in immigration policies established by her predecessor, Andrés Manuel López Obrador.

Groups of 800 and 600 migrants left the region earlier in October.

Activist Luis García Villagrán estimates about 40,000 migrants are currently stranded in southern Mexico.