President Obama has come under increasing pressure to secure the US-Mexico border US troops sent to secure the Mexican border have begun patrols in Arizona.
They are among 1,200 extra soldiers deployed by President Barack Obama to beef up the 1.900-mile (3,000km) frontier, a major route for drug and people smuggling.
Nearly half of these National Guards will be stationed in Arizona, whose porous desert is the most popular route for traffickers.
The operation, which began in California earlier this month, will also cover Texas and New Mexico.
Authorities say the troops will be “extra eyes and ears” for existing Border Agents. They will be armed but will not have powers to arrest.
Pressure has been growing on the US federal government to stop people and drugs entering the US illegally through Mexico. The loudest calls have been from Arizona.
Earlier this year Arizona passed tough new anti-immigration laws that were popular with voters. But the laws were put on hold by a court and opposed by the president.
Mr Obama wants to create a pathway to citizenship for illegal immigrants already in the US.
In 2006, President George W Bush sent 6,000 troops to the Mexican border to reinforce security, but they pulled out two years later.
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