Mexican President Andres Manuel Lopez Obrador said he plans to visit Mexico's southern border next week to discuss the smuggling of child migrants with local officials. 

Unaccompanied children coming to the United States is still a growing concern for U.S. officials. With that, the U.S. asked Mexico and other countries in Central America to help them stop the surge of child migrants arriving at the U.S.-Mexico border, according to an Associated Press report.

The Biden administration recently made agreements with Mexico, Guatemala, Honduras, and El Salvador to use troops to stop migrant smuggling. It was criticized by human rights and migrant advocates, saying it would make it more difficult for people seeking asylum.

But in his daily news conference on Wednesday, Lopez Obrador noted that Mexico is going to reinforce the "surveillance, the protection, the care" on the southern border to protect children and defend human rights.

The Mexican president has shown photographs of a tractor-trailer rig stopped in Tuxtla Gutierrez on Tuesday that carried 149 migrants, which includes 28 minors from Honduras and Guatemala.

Vice President Kamala Harris earlier said that she would visit Mexico and Guatemala soon. President Joe Biden has tapped Kamala Harris to lead the administration's efforts to respond to the southern border's migration situation.

The vice president has been receiving criticisms from Republicans for not having yet traveled to the U.S.-Mexico border, CBS News reported.

White House press secretary Jen Psaki explained that Harris' responsibility is not the border per se, noting that it was the Northern Triangle countries and Mexico.

Kamala Harris said that they need to deal with the root causes.

"We need to deal with what's happening in the Northern Triangle and address it in a way that is about not only diplomacy but bringing our allies together," Harris said in a report.

READ NEXT: New Report: Majority of Unaccompanied Migrant Children Now With Relatives in US

Migrant Smugglers

Earlier this month, smugglers were caught on camera dropping two young children at the border. The U.S. Customs and Border Protection (CBP) released a video of two people bringing the children to the border barriers on the Mexico side on Tuesday night, ABC News Go reported. 

One Honduran mother handed herself and her son into border agents in Texas. She contracted a smuggler to ferry her son across the border after being expelled back to Mexico. The Honduran mother, Alicia Cruz, said that her son was with relatives in Texas.

"The last thing he said was 'let me go to study, work so I can help you," Cruz said as reported by Reuters. Cruz and her son are among the many who reached out to smugglers to enter the United States.

The increasing number of migrants crossing the border comes after Biden said it would not immediately expel unaccompanied minors, which is a policy shift from Trump's administration.

Stories of unaccompanied migrant children differ from each other. Some come with their parents, while others cross with friends or relatives who are not their legal guardians.

READ MORE: Biden Administration to Expedite Release of Migrant Children by Flying, Bussing to U.S. Homes

WATCH: Exploring How And Why So Many Migrants Are Crossing the Southern Border - From PBS NewsHour