WASHINGTON (Reuters) – U.S. President Donald Trump will sign a proclamation on Wednesday ordering the deployment of the National Guard to help protect the border with Mexico, Homeland Security Secretary Kirstjen Nielsen said.

Troops may be heading to the border as early as Wednesday night, Nielsen said, saying that the National Guard would support U.S. Custom and Border Protection but would not be involved in enforcement.

Nielsen spoke at a White House news briefing a day after Trump sharpened his anti-immigration rhetoric by saying he wanted to deploy U.S. military forces until his promised border wall is built.

Homeland Security Secretary Kirstjen Nielsen speaks during a press briefing on border security at the White House in Washington, U.S., April 4, 2018. REUTERS/Kevin Lamarque

“The president has directed that the Department of Defense and the Department of Homeland Security work together with our governors to deploy the National Guard to our southwest border to assist the Border Patrol,” Nielsen said. “The president will be signing a proclamation to that effect today.”

She said the administration had drafted legislation and would be asking Congress to provide the legal authority and resources to address “this crisis at our borders.”

She did not give the number of the troops to be deployed or the cost of the operation.

Nielsen said that despite steps taken by the administration, the levels of drug smuggling, illegal immigration and dangerous gang activity across the border were unacceptable.

Trump met with Defense Secretary James Mattis, Attorney General Jeff Sessions, Nielsen and other officials to discuss border issues on Tuesday.

“Until we can have a wall and proper security we’re going to be guarding our border with the military,” Trump told reporters at the White House on Tuesday, lamenting what he called “horrible” U.S. laws that left the southern border poorly protected.

On Wednesday, Trump said in a tweet: “Our Border Laws are very weak while those of Mexico andCanada are very strong. Congress must change these Obama era, and other, laws NOW!”

(This version of the story was refiled to add dropped word “but” in paragraph two)

(Reporting by Jeff Mason; Writing by Mohammad Zargham; Editing by Eric Beech and Leslie Adler)