Colombia's biggest guerrilla force said on Friday it was betrayed by its own men in last week's military rescue of Ingrid Betancourt and 14 other hostages that added to a string of recent setbacks.

The rescue of the kidnap victims - who included three American defence contractors held for years in secret jungle camps - highlighted the success of President Alvaro Uribe's U.S.-backed offensive against the guerrillas.

The group said it remained willing to negotiate a swap with the government of remaining hostages for guerrilla detainees, although negotiations with hard-liner Uribe remained bogged down over conditions for holding the exchange.

The hostages were being guarded by rebel officers Antonio Aguilar, known as Cesar, and Alexander Farfan, known as Enrique Gafas. They escorted their captives onto a helicopter that supposedly was to take them to another camp but was in fact flown by Colombian intelligence agents posing as aid workers.

Once in the air the agents disarmed the officers and informed the hostages that they were free. The FARC accused the two of betrayal without giving details of the accusation.

"The escape of the 15 prisoners on July 2 was a direct consequence of the despicable conduct of Cesar and Enrique, who betrayed their revolutionary ideals and the trust we had put in them," said the Revolutionary Armed Forces of Colombia (FARC).

The statement, signed by the FARC's secretariat, was issued on the Bolivarian Press Agency website.

Both rebels captured during the rescue are expected to be extradited to the United States to face kidnapping charges.

"If they did betray the FARC by cooperating with the government in the rescue, then they did not negotiate very well because they are looking at some long prison time in the United States," said Pablo Casas, a Bogota-based security analyst.

"The only way out for the FARC at this point is to take a more political approach to the government, which is why they say they will discuss a hostage exchange," Casas added.

Colombia said it had infiltrated the FARC for the rescue. Whether or not the FARC's charge of betrayal against the two commanders is true, last week's intelligence operation shows the guerrillas have been badly debilitated.

A record 1,600 fighters have deserted since January. The March killing of two FARC leaders, one betrayed and dismembered by a bodyguard seeking a government reward, ended four decades of government failure to hit the guerrillas' top leadership.

The FARC's long-time top commander, Manuel "Sureshot" Marulanda, died of natural causes the same month, compounding the disarray in South America's longest insurgency.

Betancourt, a French-Colombian citizen, was captured during her 2002 presidential campaign. The Americans were snatched in 2003 after their plane crashed during an anti-drugs mission.

The FARC still holds hundreds of Colombians for ransom and political leverage. But the group has lost backing - notably from one-time political ally Hugo Chavez of neighbouring Venezuela - and been pushed onto the defensive by Uribe.

The FARC says it wants to exchange 25 kidnapped soldiers, police and politicians for jailed guerrillas, but Uribe rejects the rebels' demand that he pull government troops from an area the size of New York City to set the stage for the swap.