The US Congress on Wednesday backed a controversial $1.7bn aid package to assist drug control in Colombia after a debate that highlighted a confusing array of agendas in what opponents warn could be "America's next Vietnam".

The Colombia strategy of President Bill Clinton is aimed at fighting Marxist guerrillas, drug smugglers and middle-America's growing problem with drug imports.

But both Republican and Democratic critics have accused the administration of trying to drag the US into an escalating civil war in order to address domestic political considerations.

Mr Clinton stunned observers earlier this year by proposing $1.3bn in emergency funds to help Colombia's anti-drug effort over the next two years. The amount requested for the proposed package has since grown to more than $1.6bn - an unprecedented increase from funding of just $66m in 1996 for Colombia's anti-drug smuggling efforts.

Mr Clinton and other supporters of the plan say the money is essential to halt the flow of drugs into the US.

The strategy calls for the creation of three anti-drug battalions in the Colombian army, to be backed up by more than 60 new US helicopters and other military equipment as well as US military advisers.

The units would be deployed to help eradicate coca plants grown by peasants - but the military effort would also be directed at the powerful guerrilla groups operating in the area.

Mr Clinton, signalling growing concern about being seen to be soft on drugs, elevated drug control issues last year and raised the profile of his chief anti-drug adviser, Gen Barry McCaffrey.

The general has repeatedly urged both the White House and Colombia's president, Andres Pastrana, to curb Colombia's growing cocaine production and drug lord ties with Marxist guerrillas and rightwing paramilitary groups.

Opinion polls late last year showed growing public alarm across the US about increasing drug use, and new support for US military assistance in drug producing areas. The polls played on Mr Clinton's fears of becoming the "drug president" and leaving the Democrats saddled with the Colombia problem.

More significantly, the administration's Colombia strategy became the target of extensive lobbying last year by big US defence manufacturers, including companies which make the helicopters and P-3 radar aircraft used to track and fight drug producers and smugglers. Other large US companies with interests in Colombia have also pushed for greater US involvement.

Paul Coverdell and Mike DeWine, Republican senators, summed up the view of many Republicans last week, saying the aid package was "clearly in our national interest".

But critics say the price tag is too high and will drag Washington into an ill-fated regional conflict. In a recent essay, Kenneth Sharpe and Bill Spencer say: "The new 'southern Colombia' strategy is not just futile but truly dangerous."

Mr Sharpe, co-author of a book on drug politics, and Mr Spencer, deputy director of the Washington Office on Latin America, an independent lobbying group, warn that the counter-insurgency strategy is no more likely to succeed than the counter-narcotics plan.

"The guerrillas are well-financed and well-entrenched. Even without ground troops, the Clinton plan offers a US embrace to a brutal and corrupt military that often works hand-in-glove with right-wing paramilitary groups, themselves deeply implicated in the drug trade."

The Colombia plan, which is part of a massive $9bn-plus package of emergency spending requirements, has also drawn the opposition of fiscal conservatives in both houses. The House was set complete its debate on the emergency bill on Thursday, after voting 289-130 to add $4bn for the Pentagon to the original $9bn bill. The plans still, however, have to go to the Senate.

In Colombia, meanwhile, the government of Mr Pastrana stepped up efforts to give assurances about the country's ability to handle the proposed US aid, which would form part of $3.5bn of varied foreign assistance proposed in Mr Pastrana's "Plan Colombia".