As President Trump battles with Congress over funding, four companies have been selected by the federal government to build concrete prototypes of the president’s long-promised wall along the border with Mexico.

U.S. Customs and Border Protection said Thursday that Caddell Construction Company of Montgomery, Ala.; Fisher Sand & Gravel of Tempe, Ariz.; Texas Sterling Construction Company of Houston, Texas; and WG Yates and Sons Construction of Philadelphia, Miss. have been awarded contracts.

The agency issued requests for proposals in March for multiple prototypes.

“Through the construction of prototypes, we are partnering with the industry to identify the best way to build new and replacement infrastructure along our border before we make further investments,” Customs and Border Protection Acting Deputy Commissioner Ronald Vitiello said during a Thursday press conference.

Vitiello said the agency asked for conceptual wall designs using reinforced concrete and alternative material to construct multiple wall prototypes in the San Diego, Calif. area.

“The prototypes and resulting wall infrastructure will complement the various other tools that we employ to secure our borders,” he said.

The president issued an executive order in January that called for securing “the southern border of the United States through the immediate construction of a physical wall on the southern border, monitored and supported by adequate personnel so as to prevent illegal immigration, drug and human trafficking and acts of terrorism.”

SANDERS STANDS BY TRUMP’S BORDER WALL THREAT

The Republican-controlled Congress has yet to pass a spending resolution to keep the government fully operational past Sept. 30. Trump has suggested he’s willing to shut down the government in order to get funding to build a wall on the border with Mexico.

“Believe me, if we have to close down our government, we're building that wall,” the president said during a rally in Arizona last week.