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Companies looking to bid on President Donald Trump’s proposed "big, beautiful" wall along the U.S.-Mexico border just got an extension, with the federal government on Wednesday pushing back the deadline until next week.

U.S. Customs and Border Protection (CBP) told NBC News that the deadline for potential bidders for the roughly 2,000-mile-long wall had been extended to April 4 in order to give the agency time to answer questions that companies had ahead of Wednesday’s initial deadline, and to give those companies time to consider those answers.

CBP announced requests for border wall proposals earlier this month, with threshold requirements including that the wall be “aesthetically pleasing” on its north, or U.S.-facing side.

The United States side of the U.S.-Mexico border in San Ysidro, California on Jan. 26, 2017. David McNew / AFP - Getty Images, file

Trump’s promise for a “big, beautiful wall” was a cornerstone of his 2016 presidential campaign, and he has said he wanted it to be at least 30 feet high — although he changed his mind a few times.

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The requests for prototypes included one for a solid, concrete wall and another that incorporates a “see-through” component to the wall.

Related: Federal Government Solicits Design Proposals for Border Wall With Mexico

Requirements for the proposed wall include taking into consideration Trump's call for a 30-foot-tall structure — although the CBP said it would accept designs as short as 18 feet — with anti-climb topping features, an "aesthetically pleasing" U.S.-facing side and the ability to withstand attacks from sledgehammers, torches and other tools.

The federal government will award the contract based on several 30-foot-long prototypes that will be built in San Diego.

Trump has repeatedly said that he would make Mexico pay for the wall but Mexican President Enrique Peña Nieto has continued to refute that claim.

Back in January, Trump signed an executive order directing federal funding to constructing the border wall, directing the secretary of homeland security to prepare congressional budget requests for the structure.

Related: Trump’s Wall Is Only One Potential Option for Border

That executive order also called for hiring 5,000 additional Border Patrol agents, building more facilities to detain undocumented immigrants near the Mexico border and ending “catch-and-release” protocols, where undocumented immigrants in the U.S. are not detained while they await court hearings.

Trump has given a cost estimate of $12-$15 billion for the wall, but a CNBC analysis found that it could balloon to as much as $25 billion, and that doesn't include annual maintenance, which could run as high as $750 million.

Sen. Claire McCaskill, D-Mo., said Tuesday, according to the Associated Press, that administration officials informed her staff that next year's budget will request $2.6 billion to build less than 75 miles of wall.