Hundreds of National Guard troops will begin deployment to the United States-Mexico border on Aug. 1, part of the Obama administration’s effort to increase security and stem the flow of weapons, cash and people into the United States, the administration announced Monday.

In May, President Obama pledged the deployment of 1,200 troops. More than 500 of the soldiers will go to Arizona, and the rest will go to New Mexico, Texas and California.

The announcement of a firm date comes as the debate over illegal immigration intensifies throughout the country. The White House is facing pressure to overhaul federal immigration policy after Arizona enacted a law requiring the police to question the immigration status of anyone they stop for other reasons if they suspect that the person is in the country illegally.

“These troops will provide direct support to federal law enforcement officers and agents working in high-risk areas to disrupt criminal organizations seeking to move people and goods illegally across the southwest border,” Janet Napolitano, the secretary of the Department of Homeland Security, said in a statement.