WASHINGTON (Reuters) - The U.S. Customs and Border Protection agency said on Friday it will accept proposals next month for the design of a wall to be built near the U.S.-Mexican frontier, a first step in picking vendors for President Donald Trump’s proposed border wall.

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In a document on the federal government’s website for business opportunities, the CPB said it would release a request on or about March 6 asking companies for prototype ideas for a wall to be built near the U.S.-Mexican border.

After reviewing the ideas submitted by vendors, the agency will evaluate and select the best designs by March 20, then issue a request for proposals by March 24 in which vendors would be asked to price out the cost of building the proposed wall.

The document says multiple awards for the barrier are expected by mid-April as part of the process, an aggressive schedule for a government construction project.

“It’s going to start soon. Way ahead of schedule, way ahead of schedule,” Trump told the Conservative Political Action Conference on Friday.

A spokesman for U.S. Customs and Border Protection, who spoke on condition of anonymity, said the solicitation published on Friday had “everything to do” with the wall that Trump has proposed.

The spokesman said the initial request for information was to give industry the opportunity to tell the Department of Homeland Security, which oversees CBP, what is possible in constructing a border wall.

“Once we get feedback from the vendors, we’ll look at the ones that are most feasible,” the spokesman said. That would be followed by the request for proposals to firm up exactly how much constructing the wall would cost.

A U.S. Department of Homeland Security internal report seen by Reuters this month indicated the border wall would be a series of fences and walls that would cost as much as $21.6 billion to build and take more than three years to complete.

The report’s estimated price tag is much higher than a $12 billion figure cited by Trump in his campaign and estimates as high as $15 billion from Republican House of Representatives Speaker Paul Ryan and Senate Majority Leader Mitch McConnell.

The plan laid out what it would take to seal the border in three phases of construction of fences and walls covering just over 1,250 miles (2,000 km) by the end of 2020. With 654 miles (1,046 km) of the border already fortified, the new construction would extend almost the length of the entire border.