BOGOTA -- Peace talks with the nation’s largest guerrilla group were put on edge Wednesday after the rebels defended the recent kidnapping of two policemen saying they were legitimate “prisoners of war.”

On his way to Havana to resume talks, the government’s chief negotiator Humberto de la Calle blasted the Revolutionary Armed Forces of Colombia, or FARC, and said the administration would not accept “peace at any cost.”

“We have to call things what they are: a kidnapping is a kidnapping, regardless of who the victim is,” he said. “The FARC have to answer for this act and the thousands of other kidnappings they’ve committed.”

On Friday, the guerrillas seized two policemen who had been sent to the southern Valle de Cauca province to investigate a wave of extortions. The kidnapping took the nation by surprise: In the run-up to peace talks, the guerrillas had said they would quit taking hostages for economic gain and released dozens of military and police officials, including some who had been in captivity for more than 12 years.

But on Wednesday, the group posted a brief statement on its Web site defending Friday’s actions.

“We reserve the right to take prisoner security force members who are captured in combat,” the group wrote. “They are called prisoners of war and it’s a phenomenon that occurs wherever there is conflict in the world.”

The FARC said they had repeatedly asked the government to engage in prisoner exchanges, but had been denied.

The combative tone comes after the guerrillas recently lifted a two-month unilateral ceasefire after the government refused to reciprocate.

On Wednesday, de la Calle said the group was still trying to force the government’s hand.

“They’re radically mistaken if they think that with actions like this they can force us to accept a bilateral ceasefire,” he said. “That will only happen when the final peace accord is signed.”

Defense Minister Juan Carlos Pinzón called the two policemen “heroes” and said the armed forces would keep searching for the men and step up pressure on the guerrillas. He said FARC defections were up 63 percent this year versus the same period last year. During debriefings, Pinzón said FARC defectors, including long-time gunmen, said they were being treated poorly and had lost faith in “the vision that they have to keep attacking the civilian population.”

“We’re seeing signs of crumbling within the FARC,” he added.

Founded in 1964 with Marxist underpinnings, the FARC has described itself as a revolutionary force fighting for the rural poor and the marginalized. The government and the United States consider the FARC a terrorist organization that has increasingly turned to drugs and extortion to finance its survival.

Negotiators have been meeting in Havana since November in hopes of bringing an end to the country’s 48-year-old civil conflict. The peace plan contemplates five points: agricultural reform, the guerrilla’s rights to political participation, the FARC’s withdrawal from the drug trade, the recognition of victims rights and ending the conflict.

So far, the parties have been focused on the first point and have reported making progress. But on Wednesday, de la Calle suggested there may be problems ahead.

“If the FARC doesn’t take responsibility for its victims, this process won’t be possible,” he said. “The signal they are sending with this kidnapping is contrary to what they should be doing.”