Top US officials will visit Mexico and Guatemala this week as the Biden administration battles a growing political crisis over the rising number of unaccompanied migrant children crossing the southern border.

Roberta Jacobson, Joe Biden’s adviser on the south-west border and Juan Gonzalez, the top diplomat on western hemisphere affairs in the White House’s National Security Council, would travel to Mexico on Monday, the NSC said.

While there the diplomats planned to meet with Mexican officials to work on developing “an effective and human plan of action to manage migration”, the NSC said. Gonzalez would then travel onwards to speak with Guatemalan officials and NGOs “to address the root causes of migration”.

They will be joined by Ricardo Zúñiga, a newly appointed state department special envoy for the “northern triangle” countries of El Salvador, Guatemala and Honduras.

The state department said Zúñiga, a former adviser to President Barack Obama on Latin America, would engage with those countries’ governments, as well as Mexico, on the “root causes” of the increasing number of migrants attempting to cross the US border, the vast majority of whom come from those countries.

The Biden administration has been struggling to contain and process the number of people attempting to cross the US-Mexico border, especially children, leaving the US scrambling to find adequate holding facilities.

US Customs and Border Protection said earlier this month that almost 9,500 unaccompanied children arrived in February at the south-western border. That was the highest number since May 2019 and a 62 per cent increase compared with January. At the current level, US-Mexico border crossings were on track to be the highest in 20 years, Biden administration officials have said.

While the Biden administration has repeatedly emphasised that the US southern border remains closed, it has suspended a Trump-era public health rule allowing the immediate expulsion of unaccompanied minors.

On Monday, US Immigration and Customs Enforcement announced that they had signed a short-term $86.9m contract with the non-profit division of Endeavors to provide an extra temporary 1,239 beds, as well as other services, at the border.

Henry Cuellar, a Democratic congressman for Texas, on Monday released photographs from the inside of an overflow facility for migrants in Donna, Texas, showing children sleeping on mats in proximity to each other.

When asked about photographs released by lawmakers, Jen Psaki, White House press secretary, said: “These photos show what we’ve long been saying, which is that these border patrol facilities are not places made for children.” But she added that returning children to a “treacherous journey” was “not . . . the right choice to make”.

The Biden administration has come under fire for not allowing journalists to enter the facilities. When challenged about the decision on Fox News Sunday, Alejandro Mayorkas, Biden’s top immigration official, argued that reporters could not be given access because of the coronavirus.

He added that the administration was focused on “executing operations in a crowded border patrol facility where hundreds of vulnerable migrant children are located”.

Mexico announced last week that it was tightening security at its border with Guatemala, citing the need to combat Covid-19. Since then, Mexico’s militarised National Guard police force has been deployed on the banks of the Suchiate River on the border with Guatemala, one of the main migrant crossing points.

“The main issue on the agenda will be development co-operation for Central America and southern Mexico, as well as joint efforts to ensure safe, orderly and regular migration,” tweeted Roberto Velasco, chargé d’affaires in the office of the under-secretary for North America at Mexico’s foreign ministry.

Mexico’s National Immigration Institute (INM) said the heightened border security was aimed at protecting child migrants from Central America from people smugglers. So far this year, 4,180 undocumented minors — both accompanied and unaccompanied — have been detected in Mexico.

INM said it was also using drones and night vision equipment to patrol illegal crossing routes.