Mexico warned Tuesday it would file lawsuits in U.S. courts if National Guard troops detain migrants on the border, and some officials said they fear the crackdown will force illegal crossers into more perilous areas to avoid detection.

Lt. Col. Jay Brookman, of the California National Guard, right, gestures to a map of Southern California as he gives California Gov. Arnold Schwarzenegger a briefing on possble guard troop deployment along the border, at the Capitol in Sacramento, Calif., Tuesday, May 16, 2006. Schwarzenegger was given an outline of the National Guards capabilities in fulfilling President Bush's plans to deploy National Guard troops along the border with Mexico to stem the flow of illegal immigrants. [AP]

President Bush announced Monday that he will send 6,000 National Guard troops to the 2,000-mile U.S.-Mexico border, but said the troops will provide intelligence and surveillance support to U.S. Border Patrol agents and will not catch and detain illegal immigrants.

"If there is a real wave of rights abuses, if we see the National Guard starting to directly participate in detaining people ... we would immediately start filing lawsuits through our consulates," Foreign Secretary Luis Ernesto Derbez said in an interview with a Mexico City radio station.

Mexican officials worry the increased security at the U.S. border will lead to more deaths. Since the bolstered surveillance at crossing spots in Texas and California in 1994, migrants have flooded Arizona's hard-to-patrol desert and deaths have spiked.

Migrant groups estimate 500 people died trying to cross the border in 2005. The Border Patrol reported 473 deaths as of Sept. 30.

Sending the National Guard "will not stop the flow of migrants, to the contrary, it will probably go up," as people try to get into the U.S. with hopes of applying for a possible amnesty program, said Julieta Nunez Gonzalez, the Ciudad Juarez representative of Mexico's National Immigration Institute.

Nunez said she planned to ask the Mexican government to send a migrant protection force, Grupo Beta, to more remote sections of the border.

The dusty outpost near the New Mexico border has turned into a smugglers haven after the U.S. Border Patrol increased its presence on the Arizona border.

Along the border in Nuevo Laredo, Carlos Gonzalez, a 23-year old from Mexico's southern state of Chiapas, was waiting for a chance to swim across the river into Texas. He said soldiers would not stop him getting to a construction job he had lined up in North Carolina.

"Desperation gives one a lot of willpower. If they stop me 20 times, I'll arrive on the 21st," Gonzalez said resting on a street corner outside a migrant shelter.

However, Carlos Ferrera, a 27-year-old from Honduras who lost part of his arm in a recent car accident, was worried that the National Guard could push him into dangerous terrain when he crosses to get to an $8.50 an hour landscaping job in Dallas.

"The more reinforced the border is the further we will have to go to find places to get in." Ferrera said.

Mexican newspapers Tuesday characterized the decision as a hardening of the U.S. position, and some criticized President Vicente Fox for not taking a stronger stand, though Fox called Bush on Sunday to express his concerns.

Fox's spokesman, Ruben Aguilar, said Tuesday that Mexico accepted Bush's statement that the Guard troops didn't imply a militarization of area, and that Mexico remained "optimistic" that the U.S. Senate would approve an immigration policy "in the interests of both countries."

He noted Bush expressed support for the legalization of some immigrants and the implementation of a guest worker program.

"This is definitely not a militarization," said Aguilar.

Salvadoran President Tony Saca said he worried that there could be an increase in abuses against migrants because National Guard troops are trained to handle natural disasters and wars.