Republican lawmakers in the House Foreign Affairs Committee on Saturday wrote to Secretary of State Antony Blinken, demanding answers about the Biden administration’s diplomatic moves related to the growing crisis at the southern border.

While the Department of Homeland Security is the primary agency for most immigration issues, the State Department is involved with decisions related to agreements with countries south of the border -- such as the Migrant Protection Protocols (MPP) and asylum cooperative agreements (ACAs).

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MPP was a Trump-era policy that kept migrants in Mexico while they awaited their hearings, while the ACAs were agreements with Northern Triangle countries, which included arrangements for migrants to be returned and claim asylum in those countries instead. All were abolished in the early days of the Biden administration.

"The Biden administration believes there are more suitable ways to work with our partner governments to manage migration across the region," Blinken said in a statement last month on the ACAs. "The United States will build on our strong relationships and support these governments’ efforts to address forced displacement without placing undue burden on them, especially in the context of the COVID-19 pandemic.

The 23 Republican House lawmakers, led by Ranking Member Michael McCaul wrote to Blinken about their  "deep concerns" over the moves.

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"We are particularly troubled by the premature and politically-motivated decision to cancel the effective Migrant Protection Protocols with Mexico, as well as the [ACA]s with El Salvador, Guatemala and Honduras -- a serious and preventable foreign policy blunder that is exacerbating the crisis," they wrote.

The letter comes as Republicans sound the alarm about the surge in migrant numbers, which has seen more than 100,000 migrant encounters in February and a spike in unaccompanied minors -- which has left the Biden administration scrambling to open facilities to house them, and appealing for volunteers.

The administration has denied there is a crisis and blamed that it calls a "challenge" on the Trump administration’s policies for having "dismantled" asylum and immigration pathways that it says it now has to rebuild.

Republicans on Saturday focused on reports that the administration had been warned by officials in the Trump administration of ending policies like MPP and that it would lead to a surge in migrants making the journey north.

"We believe that an objective evaluation by the Administration would have concluded that the asylum agreements were stemming illegal migration flows and deterring individuals from making the dangerous journey to the United States," they write. "Instead, as Mexico’s President López Obrador has recently noted, the administration ignored the risks and, by canceling Trump’s policies, created the perception among migrants wanting to cross the border that it is now easier to do so."

The lawmakers also raised concern about Biden’s plan to invest $4 billion in a strategy to deal with "root causes" of migration in Central America, warning that it "emphasizes dollar amounts over the quality and effectiveness of U.S. foreign assistance."

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"The administration cannot address root causes in Central America and Mexico merely by throwing more money at the problem," they say.

Separately, they encourage Blinken to submit a five-year strategy to address the causes of illegal immigration "as soon as possible."

They also ask the new secretary of state what estimates are for migrant numbers in the summer, what steps the administration is taking to deter migrants from coming and how Northern Triangle countries reacted to the canceling of Trump-era agreements.

Among other answers requested of Blinken, the letter asks if funding to groups like the U.N. High Commissioner on Refugees (UNHCR) will change due to the canceled ACAs, and whether the administration has considered working with Mexico to house asylum applicants there and if there are discussions underway.

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The letter comes days after Biden stood by his moves to roll back Trump-era border protections and said he makes "no apologies" for the decisions.

"Rolling back the policies of 'Remain in Mexico,' sitting on the edge of the Rio Grande in a muddy circumstance with not enough to eat? I make no apologies for that," Biden said. "I make no apologies for ending programs that did not exist before Trump became president that have an incredibly negative impact on the law -- international law -- as well as on human dignity. And so I make no apologies for that."