US to send National Guard to Mexican border in August
US National Guard troops will begin deploying along the US-Mexico border from 1 August, officials say.
The 1,200 troops, ordered to the border by President Barack Obama, form part of efforts to tackle illegal immigration and drug-trafficking.
They will be in the four border states, with Arizona getting the largest share.
A controversial new state law is due to come into effect in Arizona on 29 July making it a crime to be in the state without without immigration papers.
Several lawsuits, including one by the federal government, have been filed challenging the legislation.
The National Guard troops would be fully operational by September, Alan Bersin, the commission of Customs and Border Protection, told a news conference on Monday.
"The border is more secure and more resourced than it has ever been, but there is more to be done," he said.
In May, President Obama announced that he would seek $500m (£350m) in new funding and deploy the troops to help secure the border.
The soldiers, who will be armed but can only fire in self-defence, will mainly be deployed to observe suspicious movement along the border and will report to Border Patrol agents.
They are to stay for a year, allowing time to hire and train more agents, officials said.
Arizona will receive 524 troops; Texas 250, California 224 and New Mexico 72, while 130 will be part of a national liaison office.
Arizona Governor Jan Brewer welcomed the administration's efforts but said the deployment did not "appear to be enough or tied to a strategy to comprehensively defeat the increasingly violent drug and alien-smuggling cartels" that operate in Arizona on a daily basis".
The new Arizona legislation will require state and local officers to query the immigration status of people stopped for a legitimate reason who arouse suspicion of being in the US illegally.
The Arizona legislature says it was forced to act because the federal government failed to do so.
The US justice department is challenging the law, arguing it as it usurps the federal administration's authority to set immigration policy.