BOGOTA, COLOMBIA, DEC. 16 -- Foreign and Colombian law enforcement officers are expressing concern that the public exchange between leaders of the Medellin cocaine cartel and the government signals a sharp drop in Colombia's commitment to the U.S.-backed campaign against drug trafficking.

"I have never felt so discouraged," said a senior law enforcement officer. "The police and the law enforcement community view this as a complete government sellout. All the progress we made in the past 18 months is going right down the tubes."

While no direct talks have taken place, the two sides have been responding to each other's proposals and modifying their positions through the media for several weeks in what the Colombian press has termed "negotiation without dialogue."

Besides the exchange, the newly elected constitutional assembly will almost certainly ban extradition and consider an amnesty for traffickers. Thus, say the officials, even if President Cesar Gaviria holds firm with the traffickers, the commitment could dissolve in the assembly.

"To say they are throwing in the towel is unfair to the police, who continue fighting and dying," said a European diplomat. "The question is, what is the government doing? We don't know, and I am not sure they do.

"This government has been taking money from {foreign countries}, promising to continue to fight narcotics trafficking," said the diplomat. "They will have a lot of explaining to do if this culminates with little or no punishment for major trafficking figures, and that international support will dry up."

U.S. and European diplomats say that while the attention of Western leaders is fixed on the Middle East, the shifts in Colombia virtually are being ignored.

The government says it is not negotiating, but showing the maximum flexibility allowed under the law to make sure the traffickers spend at least some time in prison.

"We are walking between two precipices," said a senior government official. "If we do not respond, we will be seen wasting a real chance for peace. If we do respond, we are seen as talking with terrorists."

Another senior official said Gaviria, who campaigned as a hard-liner, has not changed his position, but that the president's seeming flexibility is necessary because the drug war has grown unpopular and politically costly. "What people outside do not understand is that this is necessary to save the policy politically," the official said. "If we lose politically, then we have lost the whole policy."

Expectations of an imminent deal have been raised as the traffickers, who call themselves the Extraditables, have freed three of nine journalists they have held hostage, and sent communiques declaring a "unilateral truce" and word that the rest of the journalists probably will be freed before Christmas.

This has given rise to widespread hope here that after 16 months of fighting the traffickers, with more than 1,000 dead, peace is returning to Colombia.

Juan Gomez Martinez, a former mayor of Medellin who was elected to the constitutional assembly and is an outspoken proponent of dialogue, said in a recent interview that Colombia had suffered enough and had to seek a settlement with the Extraditables.

"Public opinion has changed radically," said Gomez, who is mediator between the families of the kidnapped journalists and the traffickers. "When I first talked about dialogue, I was an outcast. Now most people understand that the solution must be peaceful, not with bullets.

"Some say that dialogue is betraying all those killed, but you do not achieve justice by having more dead," Gomez said. "People outside the country do not understand that. We are the ones who are suffering . . . and we alone should reach a solution."

The Extraditables have said they will turn themselves in if they are assured immunity from extradition and if confession of crime and testimony against others are not made conditions of their surrender. They also demand that any incarceration be in special prisons, and guarantees that their human rights and those of their families will be respected.

In response, the government has modified its positions in ways seeming to favor the Extraditables: agreeing to ban extradition for those who turn themselves in, regardless of what they confess to; constructing special, spacious prisons to house those who turn themselves in; and investigating alleged human rights abuses by the police.

"If all these guys turned themselves in and turned over some labs, we might have an insignificant, momentary decrease in production," said a knowledgeable Western diplomat. "At the same time, indirectly, the operations will continue with the same guys behind the scenes. The government will have been taken. That is reality; the cops know it. The question is, does the government know it?"

While the United States has not publicly criticized Colombia, a senior Colombian official said next year would be rocky in U.S.-Colombian relations.

The United States is "grateful for our support {against Iraq} on the {U.N.} Security Council," the official said. "But we are off at the end of the year, and we expect 1991 to be the most difficult with the U.S. in a long time."

The issue of confession is crucial because there are no charges against most of the Extraditables, meaning the state would have no case against them, and without requirement of confession, they would be freed in a matter of days. Even Pablo Escobar, the Medellin cartel leader, has no drug-related charges pending in Colombia, although he has been indicted in several murder cases.

The government has said confession would be a condition of any negotiated surrender by traffickers. Two advisers said that despite some pressure within the president's inner circle to abolish the confession requirement, Gaviria has refused.

Colombian and foreign narcotics experts say the Extraditables are offering to turn themselves in now because they know the state cannot prove anything against them, and because over the last year they have moved much of their business out of Colombia to neighboring countries, where they are still relatively safe.

A new Interpol report says that "cocaine production is rapidly spreading to other countries, at the same time Colombians are moving their installations there. These include Bolivia, Peru, Ecuador and Brazil."

Drug enforcement authorities in Bolivia said last month that the production of refined cocaine there has jumped from almost nothing in 1989 to an estimated 100 metric tons in 1990.