A group of 40 GOP senators on Wednesday asked the Government Accountability Office to decide whether President Biden's decision to freeze more than $1 billion in congressionally approved border wall funding violates federal law.

The letter comes as an influx of migrants arrives at the U.S.-Mexico border, creating a humanitarian crisis.

The coalition led by Sen. Shelley Moore Capito, R-W.Va., noted Biden's immediate suspension of border wall construction on Inauguration Day.

In the weeks after Biden's inauguration, "operational control of our southern border was compromised and a humanitarian and national security crisis has ensued," the senators wrote.

"The President's actions directly contributed to this unfortunate, yet entirely avoidable, scenario," the letter states. "They are also a blatant violation of federal law and infringe on Congress's constitutional power of the purse."

BIDEN CAN'T KEEP UP WITH BORDER SURGE OF MIGRANT CHILDREN, CBP OFFICIAL WARNS

The senators said they believe Biden's actions "violated the Impoundment Control Act (ICA), as interpreted by your office," and are requesting the GAO's legal opinion.

Congress approved nearly $1.4 billion in border wall funding in December 2020 for fiscal year 2021 as part of former President Donald Trump's $900 billion coronavirus stimulus package.

The senators added that border apprehensions have increased since Biden took office. 

FILE - Crews construct a section of border wall in San Bernardino National Wildlife Refuge, Tuesday, Dec. 8, 2020, in Douglas, Ariz. (AP Photo/Matt York)

FILE - Crews construct a section of border wall in San Bernardino National Wildlife Refuge, Tuesday, Dec. 8, 2020, in Douglas, Ariz. (AP Photo/Matt York)

Signatories include Minority Leader Mitch McConnell, R-Ky., and the following Republican senators:

  • John Barrasso of Wyoming, 
  • Marsha Blackburn of Tennessee
  • Roy Blunt of Missouri
  • John Boozman of Arkansas
  • Mike Braun of Indiana
  • Richard Burr of North Carolina
  • Susan Collins of Maine
  • John Cornyn of Texas
  • Tom Cotton of Arkansas
  • Kevin Cramer of North Dakota
  • Mike Crapo of Idaho
  • Steve Daines of Montana
  • Joni Ernst of Iowa
  • Deb Fischer of Nebraska
  • Lindsey Graham of South Carolina
  • Bill Hagerty of Tennessee
  • John Hoeven of North Dakota
  • Cindy Hyde-Smith of Mississippi
  • Jim Inhofe of Oklahoma
  • John Kennedy of Louisiana
  • James Lankford of Oklahoma
  • Cynthia Lummis of Wyoming
  • Roger Marshall of Kansas
  • Jerry Moran of Kansas
  • Rand Paul of Kentucky
  • Rob Portman of Ohio
  • Jim Risch of Idaho
  • Mitt Romney of Utah
  • Mike Rounds of South Dakota
  • Marco Rubio of Florida
  • Rick Scott of Florida
  • Richard Shelby of Alabama
  • John Thune of South Dakota
  • Thom Tillis of North Carolina
  • Pat Toomey of Pennsylvania
  • Tommy Tuberville of Alabama
  • Roger Wicker of Mississippi
  • Todd Young of Indiana

GAO managing director of public affairs Charles Young confirmed to Fox News that the office has received the letter but added that every new request goes through a review process that usually takes several weeks.

THE WORD THE BIDEN ADMINISTRATION WON'T USE WHEN IT COMES TO THE BORDER? 'CRISIS'

Migrant children are arriving at the U.S. southern border at rates faster than they can be processed and transferred to sponsor homes, all while the Biden administration has repeatedly denied that there is a "crisis" at the border, a senior Customs and Border Protection official told Fox News. 

The number of migrant children in federal custody has surged past 4,000 with roughly 94% of beds for migrant children occupied, the source told Fox News. Migrant children are entering federal custody far faster than they are leaving it, creating an unsustainable backlog, the source said.

People surround a car as it arrives carrying food donations at a makeshift camp for migrants seeking asylum in the United States at the border crossing Friday, March 12, 2021, in Tijuana, Mexico. (AP Photo/Gregory Bull)

People surround a car as it arrives carrying food donations at a makeshift camp for migrants seeking asylum in the United States at the border crossing Friday, March 12, 2021, in Tijuana, Mexico. (AP Photo/Gregory Bull)

Customs and Border Protection announced last week that the agency encountered 100,441 individuals in February, a 28% increase over January, the agency said. Of those, 19,246 individuals were in family units, 9,457 were unaccompanied children (UACs) and 71,598 were single adults.

Earlier in March, a senior DHS official confirmed to Fox News that the number of migrant children in custody along the border has tripled in the past two weeks to more than 3,250 and that more than 1,360 had been held for longer than the allowed three days. 

MCCARTHY SAYS BIDEN HASN'T RESPONDED TO HIS REQUEST FOR BORDER MEETING, AS GOP TIES CRISIS TO HIS POLICIES 

A number of Republicans have made plans to visit the U.S.-Mexico border and get a firsthand account of what is happening.

Republicans on the House Homeland Security Committee visited the border over the weekend before Department of Homeland Security chief Alejandro Mayorkas' testimony before the committee on Wednesday.

Mayorkas released a lengthy statement on Tuesday defending the administration’s policies and suggesting it would not be changing course any time soon.

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"The situation at the southwest border is difficult," Mayorkas said. "We are working around the clock to manage it and we will continue to do so. That is our job. We are making progress and we are executing on our plan. It will take time and we will not waver in our commitment to succeed."

Fox News' Adam Shaw and Evie Fordham contributed to this report.