Colombia's military officially supports peace talks with its old foe, the leftist FARC guerrilla group, but behind the facade of unity there is uneasiness in the ranks after half a century of warfare.

After the peace talks were announced, the army's leadership publicly professed its loyalty to President Juan Manuel Santos.

"Count, mister president, on our unconditional backing and support," General Alejandro Navas, the head of the armed forces, said.

The government's negotiating team, which this month opens peace talks with the FARC in Norway, includes two former senior army and police officials: choices that have created a stir among the reserve officer corps.

"Under no circumstance will we put spokes in the wheels. It's just that we think certain things must be done to avoid repeating mistakes made in the past," said General Jaime Ruiz, president of an association of officers in the active reserve.

Colombia's last attempt at a negotiated peace with the FARC failed a decade ago, leaving bitter memories.

On that occasion, the authorities ordered the demilitarization of an entire region as part of a peace process, and then watched as the guerrillas used it to reinforce.

Ruiz insists that this time the peace process "must lead to the surrender of weapons and not just to laying them down."

He also is troubled by the notion of allowing guerrillas to go unpunished. "Some penal action against the demobilized guerrillas is necessary," he said.

Suspicions run strong within the military that the FARC, which officials say has some 9,000 combatants under arms, is seeking a temporary respite after a series of reverses that has halved its strength and killed key leaders.

"The FARC are still trying to buy time, a bit of space, while trying to obtain the status of belligerent in the eyes of the world," said retired general Harold Bedoya, a former army chief.

An outspoken opponent of the peace talks, who reflects the misgivings within the army, Bedoya says he is convinced that negotiators from the military "will withdraw because there is nothing in it for the country."

The current commander of the armed forces, General Sergio Montilla, has already accused the guerrillas of lying, notably about hostages taken during the conflict.

The FARC says it freed its last hostages in April and is holding no more captives, but Montilla says at least 60 soldiers are still missing.

"As long as they don't say things and call them by their real name," he said, it will be impossible to "build the path to peace."

The prospect of peace also worries the army because it could lead to funding cuts for an institution whose budget currently amounts to more than three percent of the gross domestic product.

Despite the rebels' diminishing strength, the ranks of the Colombian security forces have swollen to 430,000 members, up 140,000 from 1999 when the last peace talks were held.

"There are fears about a reduction in forces, which logically would affect the careers of officers and non-commissioned officers," a member of the high command of an important unit based in Bogota said, speaking on condition of anonymity.

But for ordinary soldiers, he said, the "worst fear" is to find their former enemies in their ranks as demobilized guerrillas are brought into the military.