Even as they provided military helicopters and training to Colombia, U.S. officials have insisted they were fighting drugs, not getting involved in the country's decades-old guerrilla war.

But staying out of that war could be trickier now that the United States is considering anti-terrorism aid for Colombia and its Andean neighbors.

The State Department's top counterterrorism official, Francis X. Taylor, told reporters Monday that the United States would fight terrorism in the hemisphere using "all the elements of our national power as well as the elements of the national power of all the countries in our region."

Of the 28 groups that the State Department considers terrorist organizations, only four are based in the Western Hemisphere. And three of those are in Colombia: the country's two largest guerrilla armies and the right-wing paramilitary umbrella group.

Those three will "get the same treatment as any other terrorist group in terms of our interest in going after them and ceasing their terrorist activities," Taylor told reporters at the Organization of American States, after attending a closed-door meeting on terrorism.

Taylor declined to discuss details of anti-terrorism aid because the package hasn't been completed. He told lawmakers last week that it was designed to complement last year's $1.3 billion Colombian aid package and an $882 million follow-up Andean aid plan that Congress is considering.

Much of the U.S. aid has been for helicopter and training to help Colombia's military fight guerrillas and, to a lesser degree, paramilitaries. Both partly finance their operations by protecting drug crops and traffickers.

To counter critics who warned that the United States was headed to a Vietnam-style quagmire in Colombia, U.S. officials have stressed that the aid was to fight drugs, not to help Colombia defeat the guerrillas.

Both critics and supporters of the Colombian aid have been skeptical, though, that such a distinction could be made.

"It's very difficult to separate the counter drug effort when the rebels or the insurgents are the ones that are living off the income from the drugs. How do you separate the two?" said Rep. Cass Ballenger, R-N.C., who chairs the House International Relations Western Hemisphere subcommittee.

With greater concern about terrorism since the Sept. 11 attacks, lawmakers aren't as likely to be concerned about the difference between fighting terrorists or fighting guerrillas. "I don't think they'll be that much differentiation," he said.

Rep. William Delahunt, D-Mass., said he didn't know what the State Department was planning for Colombia, but separating counterterrorism from counterinsurgency "would be a very difficult and delicate distinction to make."

Taylor last week said Colombia's largest guerrilla group, the Revolutionary Armed Forces of Colombia, or FARC, was "the most dangerous international terrorist group based in this hemisphere." Both the FARC and the National Liberation Army have been involved in bombings, kidnappings, extortion and hijackings.

Also on the terrorist list the right-wing paramilitary United Self-Defense Forces of Colombia, which has been involved in assassinations, kidnappings and massacres. The State Department and human rights groups say that Colombian security forces have collaborated with paramilitaries.

For all three groups, the terrorist activities have occurred primarily within Colombian borders -- a distinction from the Afghanistan-based al-Qaida organization blamed in the Sept. 11 attacks.

The top Democrat on the Western Hemisphere subcommittee, Rep. Bob Menendez of New Jersey, said a key question in shaping U.S. policy toward Colombian groups is whether they have been involved in attacks in the United States.

"If the answer is no, does the president's standard of this fight on global terrorism include those who may be terrorists, but not committed acts on the United States?"

If President Bush wants to go beyond pursuing terrorists responsible for the U.S. attacks, he will need to define the mission and go back to Congress for support.

"I think we're going to have to figure out how much we can absorb at one time," he said.