He will sign a border security bill to avert a government shutdown, but also act to bypass Congress and use military funds for the wall, a statement said.
Senior Democrats have responded by accusing him of committing a “gross abuse of power” and a “lawless act”, the BBC reported on Friday.
The Congress passed the bill on Thursday which does not meet Trump’s demands for wall funding. It now has to be signed by the President to become law.
The compromise legislation passed by Congress includes $1.3 billion in funding for border security, including physical barriers, but it does not allot money towards the border wall for which Trump had wanted $5.7 billion.
“The President is once again delivering on his promise to build the wall, protect the border, and secure our great country,” White House Press Secretary Sarah Sanders said in a statement on Thursday.
She added he would “take other executive action – including a national emergency – to ensure we stop the national security and humanitarian crisis at the border”.
Speaking on the Senate floor on Thursday, however, Republican leader Mitch McConnell indicated his support for the move, saying the President was taking action with “whatever tools he can legally use to enhance his efforts to secure the border”.
In a 83-16 vote, the Senate on Thursday passed the border security bill. The House of Representatives later also backed the measure, by 300 to 128.
Speaker of the House Nancy Pelosi has already suggested a legal challenge from Democrats should the President make an emergency declaration.
She and Senate Democratic leader Chuck Schumer also issued a joint statement condemning the move.
“Declaring a national emergency would be a lawless act, a gross abuse of the power of the presidency and a desperate attempt to distract from the fact that President Trump broke his core promise to have Mexico pay for his wall,” they said.
Republicans fear this will set a precedent for presidential power that Democrats can someday use to circumvent the will of Congress.