"The American people are no longer going to have to be forced to subsidize this disregard for our laws", he said.
Construction on the border wall will begin "as soon as we can physically do it", Trump told ABC News in an exclusive interview.
"This will stem the flow of drugs, crime, illegal immigration into the United States and yes, one way or another as the president has said before, Mexico will pay for it".
"It's also going to be good for Mexico", he added.
One directive dealt with building a wall along the 3,200-kilometre US-Mexican border. It was his biggest campaign promise, and just the beginning of extreme immigration reforms.
Mr Trump, is expected to sign an executive order enabling construction of the wall later on Wednesday, as he begins an immigration crackdown. The plan is expected to come in an executive order Wednesday.
"They're rapists and some I assume are good people", Trump said in June of 2015 of illegal Mexican immigrants crossing the southern border when he officially launched his presidential campaign from the lobby of Trump Tower in New York City.
The AP also notes that Trump's order will "restrict access to the United States for most refugees", which are mostly vulnerable women and children.
In order to force those governments to take back the deportees, Spicer said the administration would consider withholding visas and "use other tools" to ensure compliance.
The decree comes on the same day as Mexico's Foreign Minister Luis Videgaray was set to arrive in Washington for talks with the United States government, while Mexican President Enrique Peña Nieto is expected to meet Mr Trump next week.
On the campaign trail, he initially proposed a temporary ban on Muslims entering the U.S., which he said would protect Americans from jihadist attacks.