Victory in a battle with leftwing guerrillas at the weekend has helped the Colombian military to shine up its image in time for congressional debates in the US on whether to inject hundreds of millions of dollars into its fighting forces.

Special counter-insurgency troops and two army units repelled an advance by Colombia's most powerful guerrilla group, the Revolutionary Armed Forces of Colombia (Farc), just 50km south-east of the capital city of Bogota at the weekend. The armed forces chief, Fernando Tapias, said 44 rebels died in the fighting, along with five of his own soldiers and one policeman.

Military officials quickly presented the victory as evidence that their troops have taken on a new, professional edge after 18 months of restructuring in response to several demoralising defeats.

The latest clash comes as US legislators prepare for debates next month on an unprecedented Dollars 1.6bn aid package to fight drugs and bolster democracy in Colombia.

The White House has yet to offer a breakdown of the plan, but initial reports say the bulk of the spending will be earmarked for the armed forces, including funds for 30 Black Hawk and 33 Huey helicopters and training for two elite counter-narcotics units.

In preparation for the congressional debate the Colombian military has also sought to scrub up its spotty human rights record. In September General Tapias said the number of alleged human rights abuses attributed to the military had fallen by 98 per cent over the last three years, to 40 cases.

The military has also trumpeted its human rights training courses. In a typical session, officers are taught to evacuate wounded guerrillas along with their own injured, or to offer water to those captured in combat. By contrast, local media have cast a harsh light on human rights abuses committed by the Farc, such as sending terrified minors into battle.

Over the weekend, for example, the prominent daily newspaper El Tiempo ran a front-page photograph of army soldiers bandaging a rebel's bleeding shoulder. The same day a local broadcaster reported that Farc troops had prevented a wounded civilian from seeking medical help during a roadside firefight, and that he later had died.

But even if the military can persuade Colombians that it has transformed itself into a more effective fighting machine, it has a long way to go to persuade human rights groups that it can be trusted with a plump aid package from Washington.

In particular, monitors are concerned about links between the military and ultra-right paramilitary death squads. Paramilitaries massacre suspected rebel sympathisers with impunity in Colombia and often enjoy tacit military support.

Political analyst and the author Alfredo Rangel said the prospect of such a huge increase in foreign aid - US assistance to Colombia would triple under the two-year Dollars 1.6bn plan - might actually force the military to distance itself from the paramilitaries and their rights abuses.

"The Colombian state, and the army in particular, is obligated to present much more credible results in their fight against paramilitaries as a way to legitimise the increase in external aid," Mr Rangel said.

Others say the plan puts too much emphasis on military aid, and not enough on programmes to replace drug crops with legal ones, or to bolster an overburdened judicial system. While presented as an offensive on Colombia's booming drug trade, they say, the package could draw the US into Colombia's complex 35-year-old civil conflict, which has claimed some 30,000 lives.

Insurgents as well as paramilitaries are increasingly involved in Colombia's lucrative drug trade, blurring the line between anti- narcotics and anti-insurgency assistance.

"This (package) is being smuggled in under the rubric of the war on drugs which is an easy sell," said Winifred Tate, from the Washington Office on Latin America. But she added: "The vast majority of the aid will be for military assistance, creating a parallel armed force within the armed forces."

The aid proposal has already put leaders of the insurgents on their guard. "With the pretext of combating drug traffickers, the United States is getting more and more involved in the Colombian situation and could aggravate the conflict," Ivan Rios, Farc commander, told reporters last week.