President Donald Trump has signed a memorandum that grants new authority to US troops on the Southwest border to protect Customs and Border Protection personnel from migrants if they engage in violence, according to the Pentagon.

Department of Defense spokesperson Lt. Col. Michelle Baldanza confirmed to CNN that the Pentagon had received the memorandum.

The decision comes as a large group of migrants is nearing the US-Mexico border, having been the focus of Trump’s closing message during the midterm election. In the days and weeks leading up to the election, Trump ordered military troops to the border to assist the Department of Homeland Security with preparing for the migrants’ arrival.

Until this new authority was granted, troops were not allowed to intervene if CBP personnel came under attack unless they needed to act in their own self-defense.

Tuesday’s authorization comes after Department of Homeland Security officials said Monday that they were getitng information from “multiple sources including individuals in the Mexican government” of potential waves or groups of individuals who were discussing an incursion into legal ports of entry in California by attempting to pass through vehicle lanes.

The Pentagon has been working for the last several days on options for how troops can protect CBP. There are 5,800 to 5,900 troops assigned to the border mission.

Any potential use of force by US troops to protect CBP personnel must be “proportional,” a US official previously told CNN.

Two defense officials had also emphasized that National Guard forces activated by governors, as well as state and local civilian law enforcement authorities in a given area, should be relied on as much as possible.

All three officials were adamant that the change is not about troops firing weapons at migrants crossing the border. Instead the new rules will be aimed at providing the basic authorities to allow for protective measures.

The Pentagon said earlier this week  the mission will cost taxpayers approximately $72 million. That price tag covers the cost of deploying the approximately 5,900 active duty troops until December 15 and will increase the longer the troops are deployed.

Trump has said he will deploy as many as 15,000 troops if needed to push back against the group of migrants who are planning on asking for asylum. On Tuesday, Trump told reporters that the troops “are proud to be on the border. They are proud to be defending our nation. And we are not letting people in.”

Earlier this year, CNN reported that the Pentagon had rejected a similar request from the administration to send troops to protect CBP personnel at the border on the grounds that the soldiers would lack the proper authority to do so.

A separate defense official tells CNN that planning is underway to move some military police from Texas to California, where the majority of migrants trekking through Mexico toward the US are expected to go.

Homeland Security Secretary Kirstjen Nielsen addressed the possible movement of troops earlier Tuesday, saying the completion of some military missions had resulted in a “movement of forces.”

“There’s some missions that parts of the military have completed, so what you are seeing is a movement of forces,” Nielsen told reporters. “But as I said earlier, I have spoken with Secretary [of Defense Jim] Mattis directly and I have no doubt they will continue to partner with us in this mission until it is resolved.”