Trump's executive order to build border wall is a start

President Donald Trump has signed an executive order to push forward one of his biggest campaign promises: build a wall along the border with Mexico.

The executive order signed Jan. 25, five days after Trump's inauguration, instructs departments and agencies to "deploy all lawful means" to secure the southern border, prevent further illegal immigration and to send immigrants in the country illegally back to their countries.

The order sets forth Trump's policy to secure the border "through the immediate construction of a physical wall," to prevent drug trafficking and terrorism.

It directs the secretary of homeland security to:

"In accordance with existing law, including the Secure Fence Act and IIRIRA, take all appropriate steps to immediately plan, design, and construct a physical wall along the southern border, using appropriate materials and technology to most effectively achieve complete operational control of the southern border."

The order defines "wall" as "a contiguous, physical wall or other similarly secure, contiguous, and impassable physical barrier."

It also asks the department to identify and allocate sources of federal funds for the planning, design, and construction of the physical wall, and to prepare congressional budget requests for the current and upcoming fiscal years.

In an interview with ABC News' David Muir aired Jan. 25, Trump said wall construction would start in months.

At a press briefing, Trump's press secretary Sean Spicer said plans for the wall will kick off with funding already available, and that Trump will work with Congress for additional funding.

"There are a lot of funding mechanisms that can be used," Spicer said. "At this point, his goal was to get the project started as quickly as possible using existing funds and resources that the department currently has, and then to move forward and work with Congress on an appropriation schedule."

Spicer also affirmed the president's plan to have Mexico pay back for the wall, saying it would happen "one way or another."

"A nation without borders is not a nation. Beginning today, the United States of America gets back control of its borders, gets back its borders," Trump said Jan. 25 at the Department of Homeland Security.

On Jan. 23, Mexican President Enrique Peña Nieto issued 10 objectives his government will seek in negotiations with the United States, among them opposition to a wall. "While Mexico recognizes the rights of every sovereign nation to guarantee its security, Mexico does not believe in walls," Peña Nieto said.

There are 702 miles of fencing along the nearly 2,000-mile U.S.-Mexico border. The fencing includes 652 miles of primary fencing, 36 miles of secondary fencing and 14 miles of tertiary fencing, according to U.S. Customs and Border Protection.

"If Congress acts to fund the construction of Trump's border wall and spares no expense, then it could be done very quickly," said Alex Nowrasteh, an immigration expert at the libertarian Cato Institute. "However, previous government attempts to build fences were behind schedule and over budget."

Other experts have told us it could take years to build a border wall.

Trump's pledge is to build a wall and have Mexico cover the costs. While Trump is moving forward on his promise, the wall is yet to be built and Mexico has not provided funds. We rate this promise, In the Works.