Washington  - One day before President Barack Obama travels to Mexico, the administration named Alan Bersin to lead efforts to police the United States' southern border and announced a new clampdown on Mexican drug gangs.

Bersin, who served in a similar capacity under former president Bill Clinton, will lead the effort to make our borders safe while working to promote commerce and trade," Homeland Security Secretary Janet Napolitano said during a visit to El Paso, Texas.

The White House meanwhile said it was sanctioning three Mexican drug cartels, allowing the Treasury Department to seize and block financial assets of the Sinaloa Cartel, Los Zetas and La Familia Michoacana.

Obama will meet with Mexican President Felipe Calderon Thursday. The growing death toll in Mexico, where the military has been enlisted to fight the drug gangs, and US aid to the effort is expected to be at the top of their agenda.

The United States last month announced a huge expansion of its cooperation with Mexican police to help limit the illicit drug trade, including sending hundreds more US law enforcement officials and funds to the border.

White House spokesman Robert Gibbs said freezing the assets of drug cartels was part of that effort.

"Today's action underscores the US government's support for President Calderon's courageous attack on the cartels and our attempts to attack the financial underpinnings of Mexico's cartels, believed to generate billions of dollars annually," Gibbs said. (dpa)