California Gov. Jerry Brown has agreed to deploy 400 National Guard troops at President Donald Trump's request, but not all will head to the U.S.-Mexico border and none will enforce federal immigration enforcement.

A letter sent Wednesday to the Trump administration by Brown says the California troops will focus on combating transnational drug crime, firearms smuggling and human trafficking.

The Democrat says the California troops will not help build a wall or "detain people escaping violence and seeking a better life."

Trump wants up to 4,000 troops sent to the border to combat illegal immigration and drug trafficking.

Brown says the California Guard members may be deployed at the border, the coast and elsewhere statewide.

Brown's office says the deployment will happen pending review and approval by the federal government.

Meanwhile, the Arizona National Guard also plans to offer support at the U.S.-Mexico border for maintenance, repairs and surveillance but not law enforcement.

Maj. Gen. Michael McGuire says some of the 338 guardsmen and women being deployed will be armed for self-defense.

But they will mainly be called on for reconnaissance and operations support. Their tasks will include monitoring remote areas, providing air transportation for humanitarian aid or Border Patrol agents and fixing sections of fencing.

The Republican governors of Arizona, Texas and New Mexico committed 1,600 Guard members to the border after a request from President Donald Trump

Attorney General Jeff Sessions has directed federal prosecutors to put more emphasis on charging people with illegal entry, including those entering the United States for the first time.

(The Associated Press contributed to this report.)