By Jon Herskovitz

AUSTIN Texas (Reuters) - The Mexican government has condemned the deployment of Texas National Guard troops to the U.S.-Mexican border, saying Governor Rick Perry authorized the move for political purposes.

"Mexico underscores that it is irresponsible to manipulate border security for political reasons," said the statement from the Mexican government and sent by its embassy in Washington on Thursday.

Perry, seen as a possible contender for the 2016 U.S. Republican presidential nomination, said he was sending up to 1,000 troops to the Mexican border to deter criminal activity caused by drug cartels, and accused President Barack Obama of not doing enough to secure the border.

"The unilateral measure taken by the government of Texas is undoubtedly mistaken and does not contribute to the efforts in which our two countries are engaged to build a safe border and create a solution to the phenomenon of migration," the Mexican statement said.

Perry said the deployment, which started in mid-August and is expected to cost at least $12 million a month, was needed because U.S. Border Patrol resources were being strained in managing a surge of children from Central America illegally crossing into the United States.

The Texas National Guard troops are working with the state's law enforcement in support roles, he said.

Critics have questioned the spending, saying data shows the flow of children has slowed, more U.S. Border Patrol agents have been assigned to the border region and the National Guard will not have the power to arrest, which raises questions about what the troops will do.

The number of children crossing illegally on their own into the United States dropped 70 percent from June to August, Homeland Security Secretary Jeh Johnson said on Monday.

(Reporting by Jon Herskovitz; Editing by Mohammad Zargham)