The United States released another $99 million on Wednesday for equipment to fight warring Mexican drug cartels, bringing available funds for Mexico's anti-narcotics aid to almost $300 million.

U.S. Ambassador Tony Garza said the money would go toward buying planes and inspection equipment for the Mexican military, but added that the hardware may not arrive until the end of this year, due to legal checks and logistics.

The U.S. Congress approved $465 million in drug-fighting aid for Mexico and Central America in June, the first installment of a $1.4 billion package pledged by U.S. President George W. Bush during a visit to Merida, Mexico, in March 2007.

The process has moved slowly despite a surge in drug violence in Mexico because the United States wants assurances that the equipment will not end up in the hands of corrupt police working for drug gangs.

Mexican President Felipe Calderon has urged Washington to support his army-led crackdown on drug lords in a war that killed about 5,700 people last year, fueled by smuggled U.S. weapons.

Calderon has dispatched some 45,000 troops across Mexico to try to restore law and order, spending around $7 billion on the three-year military crackdown.

The so-called Merida Initiative should pay for inspection equipment like scanners, helicopters and surveillance aircraft as well as drug detection dogs. It will also fund police training in Mexico.