BY JUAN O. TAMAYO

 BOGOTA -- A recent guerrilla attack on a rural outpost that left 13 Colombian
 police dead has prompted a call to change the rules of engagement to allow the
 use of U.S.-controlled helicopters in cases where they could make a life-or-death
 difference for government forces.

 The Black Hawk helicopters, piloted by Colombian police, are supposed to be
 used only for anti-narcotics operations, but critics of U.S. involvement in the
 violence-ridden Andean nation have warned repeatedly of the danger of deepening
 American participation in the fight against leftist guerrillas.

 ``At the minimum, we ought to carve out a humanitarian exception for the use of
 Black Hawks in cases . . . where there is a potential imminent loss of life,'' Rep.
 Ben Gilman, R-N.Y., chairman of the House International Relations Committee,
 declared in a letter made public Monday.

 His complaint was prompted by the death of 13 policemen in a guerrilla attack 10
 days ago, as three UH-60 Black Hawk helicopter gunships sat nearby, unused.
 The U.S.-provided choppers were a mere 20-minute flight away from the town of
 Roncesvalles while the battle raged, Gilman said in a letter to Secretary of State
 Madeleine Albright.

 DOWNPLAYS INCIDENT

 National Police Chief Gen. Luis Ernesto Gilibert tried to downplay the controversy
 stirred here by Gilman's comments, saying that the gunships could not have flown
 at night, when the fighting took place.

 Gilibert and the U.S. Embassy here also denied Gilman's charge that the mission
 had vetoed a police request to send a Black Hawk to defend another police unit
 that suffered 22 dead in an April rebel attack in Chocó province.

 The Roncesvalles and Chocó incidents go to the heart of concerns that the rapidly
 expanding U.S. aid to Colombia for counter-narcotics operations might entangle
 Washington in a guerrilla war in a country twice the size of Vietnam.

 President Andrés Pastrana's government is fighting both an estimated 26,000
 leftist and rightist guerrillas and a narcotics industry that produces most of the
 cocaine and much of the heroin now reaching U.S. markets.

 U.S. OPERATIONS

 But Congress has restricted U.S. aid -- including a $1.3 billion package approved
 earlier this month -- to counter-narcotics operations even though rebels regularly
 protect coca and poppy plantations and laboratories.

 Gilman wrote Albright that he decided to try to ease some of the restrictions after
 Gilibert ``raised concerns about this policy with me during the police chief's visit
 to Washington last week.

 Three Black Hawks were based in Neiva, a town 80 miles from Roncesvalles in
 northern Colombia, when the Revolutionary Armed Forces of Colombia, or FARC,
 attacked the police outpost on the night of July 14.

 Thirteen defenders ran out of ammunition during the overnight battle and tried to
 surrender at dawn but were executed by the rebels, a policeman who survived told
 reporters afterward.

 By the time police reinforcements arrived one day later, after fighting their way
 through guerrilla ambushes on mountain roads, the town of 5,000 people 110
 miles southwest of Bogotá was in ruins.

 The police-piloted Black Hawks, armed with rapid-fire Gatling guns, could have
 reached the town in 20 minutes to attack the guerrillas, deliver ammunition to the
 policemen or evacuate them, Gilman said.

 But the craft were officially owned by the U.S. State Department and limited by
 U.S. rules to escorting crop-dusters spraying herbicides on poppy plantations in
 the nearby Andean mountains.

 Gilibert did not ask for embassy permission to send the Black Hawks to
 Roncesvalles because of the mission's alleged refusal to send the gunships to
 rescue the Chocó unit in April, said a senior congressional staffer involved in the
 debate.

 ``Since the U.S. Embassy [in Bogotá] maintains the absurd fiction that U.S. aid
 can only be used for counter-narcotics purposes, the Black Hawks were not
 called in, Gilman said in a statement Friday.

 DENIALS ISSUED

 Gilibert, apparently trying to defuse the controversy, told reporters in Bogotá
 Monday that ``at no time has the U.S. embassy told us that we could not use
 these aircraft.

 An embassy statement echoed the denial, saying that the Black Hawks are
 under the operational control of the police and that there is no requirement that
 the police seek embassy approval for missions.

 Gilibert, named police chief earlier this month, said he understood the aircraft
 could not be used for war but ``would not hesitate one instant to use the aircraft
 for humanitarian missions.''

 Gilman has been a staunch supporter of increased U.S. aid to Colombia despite
 concerns the money would ensnare Washington in Colombia's 35-year-old
 guerrilla war and increase human rights violations by the security forces.

 ``This [Roncesvalles] case is going to force a new definition of the rules of
 engagement because it is so egregious, the congressional staffer said in a
 telephone interview.

 AID TO ARRIVE

 The debate over the rules of engagement is expected to grow even more heated
 with the arrival of the $1.3 billion U.S. aid package, which includes 18 more Black
 Hawks, 42 older UH-1H ``Huey helicopters and training for two new army
 battalions -- all strictly limited to counter-narcotics missions.

 The helicopters and counter-narcotics battalions will be allowed under U.S. rules
 to engage guerrillas only in self-defense or if the rebels try to protect coca or
 poppy fields or refining laboratories.

 ``If, on the other hand, the guerrillas are not engaged in any narcotics activities
 and they don't fire first, the security forces can't fire on them, said the senior
 congressional staffer. ``Isn't that bizarre?