United States National Guard troops patrol along the U.S. and Mexico border in Nogales, Arizona October 8, 2010. The troops are part of a 1,200 soldier deployment authorized by President Barack Obama to patrol against illegal immigrants and drug smugglers. Arizona will receive 560 troops to protect the border. REUTERS/Joshua Lott (UNITED STATES - Tags: MILITARY SOCIETY CRIME LAW POLITICS) - GM1E6A90N6M01

PHOENIX (AP) — President Donald Trump said Thursday that he wants to send 2,000 and 4,000 National Guard members to the U.S.-Mexico border to help federal officials fight illegal immigration and drug trafficking.

Trump’s comments to reporters on Air Force One were his first estimate on guard levels he believes needed, and would be a lower number of troops than the 6,400 National Guard members that former President George Bush sent to the border between 2006 and 2008.

Asked about the cost, Trump said his administration was looking at it.

Trump said he plans to keep the guard members there until a “large portion of the wall is built.”

Earlier Thursday, Ronald Vitiello, the U.S. Customs and Border Protection’s acting deputy commissioner, cautioned against a rushed deployment.

“We are going to do it as quickly as we can do it safely,” Vitiello told Fox News Channel.

He said that guard members would be placed in jobs that do not require law enforcement work, an apparent reference to undertaking patrols and making arrests.

The National Guard in Texas expressed support, but said in a statement that deployment remained in “very early planning stages.” The Republican governors of New Mexico and Arizona have also backed the deployment. It remained unclear Thursday how Democratic California Gov. Jerry Brown would respond to Trump’s call.

In Washington, Marine Lt. Gen. Kenneth F. McKenzie told reporters at the Pentagon that it has not yet been determined how many, if any, of the troops participating in the border security operation will be armed.

With troops in all states, the National Guard has been called on by past presidents and governors to help secure U.S. borders, and the Texas contingent said it had “firsthand knowledge of the mission and operating area” that will allow it to move seamlessly into the new role.

Trump ordered the deployment because “we are at a crisis point” with illegal immigration, Secretary Kirstjen Nielsen of the Department…