LOS ANGELES (CBSLA/AP) – President Donald Trump Thursday morning commended California Gov. Jerry Brown for agreeing to send National Guard troops to the U.S.-Mexico border.

Gov. Brown “is doing the right thing and sending the National Guard to the Border,” the president wrote on Twitter. “Thank you Jerry, good move for the safety of our Country!”

On Wednesday, Gov. Brown agreed to deploy 400 troops to help with an existing program to combat transnational drug crime, firearms smuggling and human trafficking. About 250 California National Guard troops are already participating, including 55 at the border.

In a letter to the Trump administration, Brown emphasized the troops will not assist with border wall construction or immigration enforcement.

“Let’s be clear on the scope of this mission,” Gov. Brown wrote. “This will not be a mission to build a new wall. It will not be a mission to round up women and children or detain people escaping violence and seeking a better life.”

Not all the deployed troops will be going to the border. Some will be going to the coast and other locations statewide.

Federal law, notably the Posse Comitatus Act of 1878, sharply limits military involvement in civilian law enforcement, creating a supporting role for the Guard. The Pentagon said last week that Guard troops won’t perform law enforcement functions or interact with people detained by border authorities without its approval.

Unlike Republican governors in other border states, Brown disagreed with Trump’s portrayal of a border spiraling out of control, noting that Border Patrol arrests fell to the lowest level last year since 1971 and that California accounted for only 15 percent of the agency’s arrests on the Mexican border.

“Here are the facts: there is no massive wave of migrants pouring into California,” Brown wrote the Trump Cabinet members.

Trump said last week he wants to send 2,000 to 4,000 National Guard members to the border, issuing a proclamation citing “the lawlessness that continues at our southern border.”

Texas, Arizona and New Mexico have committed at least 1,600 Guard members to Mr. Trump’s effort. Brown’s 400 brings the total to 2,000.

In March, during his first visit to California since becoming president, Mr. Trump was critical of Gov. Brown while inspecting border wall prototypes south of San Diego.

“I think Gov. Brown has done a very poor job running California,” Trump said. “They have the highest taxes in the United States. The place is totally out of control. You have sanctuary cities where you have criminals living in the sanctuary cities. And then the mayor of Oakland goes out and notifies when ICE is going in to pick them up.”

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)