Colombia on Thursday was to resume peace talks with FARC guerrillas aimed at ending the half-century conflict despite the kidnapping of two police officers by the leftist insurgent group.

"The order of the president (Juan Manuel Santos) to the police is to keep pursuing the FARC. The order to this delegation is to continue working on a deal to end the conflict. We will not be diverted from this objective," chief government negotiator Humberto De la Calle said late Wednesday.

The Revolutionary Armed Forces of Colombia (FARC) confirmed earlier Wednesday that it had captured two police officers and were holding them as "prisoners of war," in a move that could undermine the peace talks.

The policemen were captured on Friday in the southwestern province of Valle del Cauca, the first kidnapping by the FARC since the rebel group freed what it said were its last 10 captive police and soldiers.

A FARC statement said the pair are "prisoners of war" and repeated a pledge not to resume kidnappings for ransom, a practice it vowed to end a year ago.

In its latest statement, the guerrilla group drew a distinction between the capture of security forces and kidnappings for ransom, in the past a major source of income for the rebels.

The FARC "has made a commitment in terms of not carrying out any more detentions of an economic character," it said.

"At the same time, we reserve the right to take prisoner members of the security force who have surrendered in combat."

"They are called prisoners of war, and this phenomenon occurs in any conflict in the world," it said.

However, late Wednesday authorities said three engineers had gone missing in a rural area in southern Colombia, in what could be a fresh kidnapping of civilians by the leftist militants.

The policemen's capture came five days after the FARC ended a unilateral two-month-long ceasefire that it had declared at the start of peace talks in Havana.

Those talks, the first in a decade after three previous failures, resume on Thursday after a weeklong recess.

"We are going to Havana to end the conflict, which is what we agreed to," De la Calle said earlier, in Bogota.

"If that's not so, tell us now, and don't waste the time of the Colombian government."

Colombia's Vice President Angelino Garzon had warned on Sunday, after the policemen were taken prisoner, that a resumption of hostage-takings by the FARC could undermine the peace talks.

In Washington, Santos's brother also warned that the hostage takings could undermine confidence in the peace process, which he said needed to move more swiftly to remain credible.

"Otherwise, the sense that this is something different will evaporate," said Enrique Santos, a former editor of the newspaper El Tiempo.

"They haven't even begun to go deeper on the first point, agrarian issues, on the six-point agenda," he said at a Washington think tank, adding that he was concerned the rebels were stalling in order to reposition themselves internationally.

Still, he said, there have been "signs of progress and a significant change in tone and language."