Members of the National Guard work on construction of a border wall between Arizona and San Luis Rio Colorado, Mexico, in 2006. President Donald Trump has pledged to build a wall along the entire U.S.-Mexico border, though the details remain unclear. Credit: David Maung/Associated Press

The Trump administration has pushed back the date for when U.S. Customs and Border Protection will start accepting design proposals for a border wall, with no firm date in sight, according to a federal government contracting website.

Contradicting earlier statements by President Donald Trump that construction plans are ahead of schedule, Customs and Border Protection announced Thursday that it will release a formal request for proposals “not before” March 15. The agency reaffirmed that design prototypes should be for a 30-foot-tall concrete barrier that meets requirements for “aesthetics, anti-climbing and resistance to tampering or damage.”

In posting the announcement to the government contracting site, fbo.gov, the agency has delayed its formal request for the second time in two weeks. When first announced on Feb. 24, the agency said the bidding process was to begin on March 6. Last week, the agency postponed the opening of bid proposals to March 8, with final proposals due by May 3.

“The Dept. of Homeland Security, Customs and Border Protection (CBP) appreciates the many expressions of interest received concerning the solicitation and provides this update to ensure all interested parties are informed of the status of the solicitation,” the agency said in the announcement this week. “The dates for receipt of responses to the two phases of this procurement will shift accordingly.”

Trump has said wall construction can be done quickly and for much less than some estimates that have pegged the cost as high as $40 billion. But a steady stream of leaks shows a different picture.

An internal Customs and Border Protection assessment estimated a $21.6 billion price tag to build the wall while a proposal to ask Congress for supplemental funds to build a wall calls for $1 billion, far below cost estimates.

The delays come as Customs and Border Protection statistics released this week show unauthorized border crossings are down 40 percent, potentially undermining a sense of urgency to build more fencing.

Congress has also been skeptical of the need for a wall, considering its potential cost. The Department of Homeland Security has not responded to a request from a top Democrat on the Senate homeland security committee for information pertaining to the wall.

U.S. Sen. Claire McCaskill, D-Mo., sent a letter to Homeland Security Secretary John Kelly on Feb. 16, asking for information on wall plans, along with details related to Trump’s executive orders on immigration and border security with no response, McCaskill spokesman Drew Pusateri said.

Andrew Becker can be reached at abecker@revealnews.org. Follow him on Twitter: @ABeckerReveal

Andrew Becker is a reporter for Reveal, covering border, national and homeland security issues, as well as weapons and gun trafficking. He has focused on waste, fraud and abuse – with stories ranging from border corruption to the expanding use of drones and unmanned aerial vehicles, from the militarization of police to the intersection of politics and policy related to immigration, from terrorism to drug trafficking. Becker's reporting has appeared in The Washington Post, the Los Angeles Times, The New York Times, Newsweek/The Daily Beast and on National Public Radio and PBS/FRONTLINE, among others. He received a master's degree in journalism from UC Berkeley. Becker is based in Reveal's Emeryville, California, office.