The US expects the helicopters to be used against drugs
US Ambassador Anne Patterson delivered the helicopters to a jubilant President Andres Pastrana, along with support equipment and a pledge to train Colombian pilots.
A Roman Catholic priest sprinkled holy water toward the helicopters as Ms Patterson, Mr Pastrana, Colombian troops and American civilian helicopter mechanics looked on.
Joint effort
"We will continue working together to liberate Colombia, the region and the hemisphere from narcotics," Ms Patterson said.
The Colombian president thanked the United States for understanding that the fight against drug trafficking was a joint effort.
The shipment is part of Plan Colombia, President Pastrana's scheme to solve the country's ills, to which former US President Bill Clinton gave $1.3bn of mainly military aid.
US aid is not about to stop there, as President George W Bush has pledged more than $600m to continue the war on drugs in South America, of which Colombia will receive the lion's share.
While the US ambassador made it clear the helicopters were to be used on drug crops, the fields are protected by two Marxist guerrilla armies and rival paramilitary right-wing forces, and there is concern that the gift will get the US embroiled in Colombia's civil conflict.
Cocaine destroyed
At the same time the United States wants to broaden its war against terrorism, particularly away from purely Muslim targets, to ward off criticism that the terrorism crusade is really against Islam, says the BBC's Colombia correspondent Jeremy McDermott.
The new helicopters, worth $14m apiece, will not be used before May, after Colombian crews complete flight training, a Colombian army Colonel, Carlos Alberto Murillo, told the Associated Press.
He said they would then accompany a brigade of US-trained Colombian troops.
Ms Patterson said that last year, Colombia's American-trained counter-narcotics troops destroyed nearly 1,500 laboratories that help produce cocaine, and almost 60 tonnes of cocaine.
And US crop dusters, protected by American helicopters, destroyed 232,000 acres of coca plants, she said.
Our correspondent says Colombia is balanced on a knife's edge at the moment, as President Pastrana has until 20 January to decide whether to continue a peace process with the country's largest rebel group.
If the talks fail and the country plunges into open war, the US may find it difficult not to come to the aid of the beleaguered Colombian government, be it in the name of the war against drugs or against terrorism.