A view of the US-Mexican border fence at Playas de Tijuana. (Photo by Justin Sullivan/Getty Images)

Taking a step toward fulfilling the president’s most prominent campaign promise, the Trump administration is soliciting ideas for its forthcoming wall with Mexico.

A presolicitation posted on the federal government’s contracting site requests “the design and build of several prototype wall structures in the vicinity of the United States border with Mexico.”

“We’re building the wall,” President Donald Trump said Friday during a speech at the Conservative Political Action Conference. “In fact it’s going to start very soon. Way ahead of schedule. It’s way, way, way ahead of schedule.”

Less than a week after taking office, Trump signed an executive order stating his policy to “secure 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.”

Two members of his cabinet, Secretary of State Rex Tillerson and Homeland Security Secretary John Kelly, were in Mexico City on Thursday. During a sometimes tense press conference, the wall never came up. At his confirmation hearing, Kelly said that, while he likes the idea of a wall, “a physical barrier in and of itself will not do the job.”

Despite Trump’s pledge on the campaign trail that Mexico would pay for it, our neighbor to the south has consistently pledged that it will not contribute to the construction of a wall on the 1,989-mile border. Already, there’s fencing of some kind on about 600 miles of it.

While Trump says it will cost about $12 billion to have an end-to-end wall, estimates from Reuters based on internal reports from the Department of Homeland Security put the price tag closer to $21.6 billion, which includes the money it would take to purchase the private land on which it’ll be built. Yearly maintenance would cost an additional $750 million annually, per Politico, and there would also be additional hiring for more border agents.

So where exactly will that money come from? House Speaker Paul Ryan (R-WI), who toured the Texas border this week, and other Congressional republicans have indicated they’ll ante up the funds for it.

The notice wants the first concept papers from bidders by March 6, and states that “multiple awards are contemplated by mid-April for this effort.”