We're spending an awful lot of money with wonderful intentions. But the results are still negligible

Senator Patrick Leahy

The American Secretary of State, Colin Powell, defended the government strategy, but he admitted that more had to be done to reduce the demand for the drug.

He also denied that the US is supporting paramilitary groups, and said the Colombian authorities had to show their commitment towards human rights in the anti-drugs efforts.

At an earlier hearing in the Senate, US Coast Guard Commander Admiral James Loy said that while seizures of drugs had increased markedly last year, their flow increased even more.

The service was unable to meet its target of a 13% seizure rate, he added.

Mr Loy said that Coast Guard vessels were unable to keep pace with the faster boats now used by traffickers.

'Worthwhile investment'

Mr Powell defended the US decision to allocate over $800m to combat trafficking in Colombia and neighbouring countries.

US funds have gone towards training Colombian troops

The funds are in addition to $1.3bn already provided for Plan Colombia.

The new programme calls for promoting alternative crops, improving infrastructure, fighting corruption and strengthening democracy in Colombia, Ecuador, Peru, Bolivia, Brazil and Venezuela.

"I think we can make a case that this is a worthwhile investment in our overall drug strategy but also in our overall development strategy," Mr Powell said.

But Mr Leahy was sceptical: "I see it more as a case where we're spending an awful lot of money with wonderful intentions...," he said.

"But the results are still, I believe, negligible."

Other senators expressed concern that the Defence Department was planning to reduce its role in the drugs war.

Iowa Republican Chuck Grassley said that he was anxious to hear the results of a Pentagon strategy review ordered by Defence Secretary Donald Rumsfeld, following "rumblings of ... desire to reduce their involvement".