U.S. Defense Secretary Robert Gates has endorsed the efforts by Colombian President Alvaro Uribe Velez to negotiate the release of hundreds of hostages held by militant groups in his country, including three Americans who have been held for more than four years. VOA's Al Pessin reports from Bogota.

Secretary Gates visited a Colombian Army training base Wednesday afternoon, where he was treated to a display of the prowess of Colombian special forces. In this exercise, they demonstrated how they would attack and clear a guerrilla camp.

But later, Secretary Gates cautioned against any such move, to free the hundreds of hostages held by Colombia's FARC guerrillas and other groups. He said hostage rescues always require careful planning and high quality intelligence, and even then are always iffy.

He cited his own experience trying to get American hostages in Lebanon released in the 1980s. Secretary Gates said the safe return of the FARC hostages is the top priority, and that will require more patience.

He endorsed a controversial effort by President Uribe to try to reach what has become known as a 'humanitarian agreement' for the release of the hostages. The plan would reportedly involve some exchange of government prisoners for the hostages, and Venezuela's President Hugo Chavez has become involved in the effort in recent weeks.

Secretary Gates indicated he is not bothered by the Venezuelan leader's involvement in the process.

"I think any opportunity that comes along, that creates an environment in which the FARC will make that decision, is to be examined very closely," said Robert Gates.

But at the same time, Secretary Gates indicated there are limits to any such deal, and that President Uribe agrees.

"President Uribe has assured me that there are limits on what he will and will not agree to as part of this possible agreement," he said. "And I'm satisfied with those limits."

On Wednesday, President Uribe issued a statement indicating he does not want two FARC guerrillas imprisoned in the United States released as part of any deal. And later, on his aircraft, Secretary Gates told reporters he and President Uribe had discussed, in his words, how counterproductive it is to release convicted criminals in exchange for hostages.

Secretary Gates also praised the progress Colombia has made in recent years to establish security, professionalize its military and bring criminals and terrorists to justice. He said in coming years, Colombia will have to continue that work with less U.S. assistance, but he also warned against a move by some members of the Congress to make sharp cuts in aid to Colombia - a move he said would be a serious mistake.