The number of U.S. troops in Colombia (search) will double to 800 under new legislation aimed at ratcheting up the fight against guerrillas and criminals financing themselves through drug trafficking (search), kidnapping and extortion.

The number of American civilian contractors paid out of U.S. funds also would rise to a maximum of 600 from the current limit of 400.

The increases were approved as part of the fiscal year 2005 defense authorization bill passed by lawmakers in an unusual Saturday session.

Some lawmakers have said they are worried that piece-by-piece increases in assistance there could draw the United States into a quagmire like Vietnam.

The United States is funding a $3.3 billion, five-year military aid package known as Plan Colombia, under which Colombian forces receive training, equipment and intelligence to root out drug traffickers and fumigate coca crops.

Saturday's measure was aimed at supporting a unified campaign by the Colombian government "against narcotics trafficking and against activities by organizations designated as terrorists," the bill said, naming the groups Revolutionary Armed Forces of Colombia (search), the National Liberation Army (search), and the United Self-Defense Forces of Colombia (search(AUC).

The bill restates the standing restriction against Americans engaging in combat operations in Colombia except when acting in self defense or attempting rescue operations.

Rebels hold dozens of hostages, including Colombian politicians, government soldiers and three American military contractors seized in early 2003 after their plane crashed in a southern rebel stronghold.

The legislation also orders the defense and state departments and the CIA to send an unclassified report to Congress in two months detailing any relationships between Colombian groups and foreign governments or groups that the United States as designated as terrorists.