MARGARITA MARTINEZ
  Associated Press

  IN THE MOUNTAINS OF NORTHWEST COLOMBIA - Clad in camouflage uniforms and carrying assault rifles, the fighters led by a commander with the nom de guerre Rodrigo hid in a village nestled amid lush green mountains and prepared for battle.

  This time, however, the Colombian paramilitary fighters were getting ready to face former paramilitary friends instead of their traditional rebel foes.

  The country's paramilitary umbrella group - the right-wing United Self-Defense Forces of Colombia, or AUC - has threatened to attack Rodrigo's smaller
  paramilitary faction if he refuses to participate in a cease-fire and ongoing peace talks with the government.

  The armed standoff, which could pit Colombia's outlawed paramilitary groups against one another, is threatening to widen Colombia's civil war.

  "In this war we are prepared to die for our ideals, even if we must fight against those who were once our allies," Rodrigo said, refusing to join peace talks.

  It was unclear if the threat by AUC commander Carlos Castano, reported by the Metro Block's commander, was a bluff.

  But analysts have long warned of the prospect that Colombia's warring factions - two leftist rebel armies and the handful of paramilitary groups - might
  splinter.

  If that happens, not only might more blood be shed in a war that already claims 3,500 lives each year, but peace agreements would be much harder to
  attain.

  The AUC, which rose in the 1980s to counter rebel extortion and kidnappings in rural areas where government troops had little or no control, entered
  peace talks with the government after declaring a cease-fire in December. The Metro Block refused to participate, saying it would negotiate with the
  government only if the rebels put down their arms.

  Nearly 1,200 of Castano's fighters have reportedly been deployed near this region northeast of Medellin, Colombia's second-largest city, to attack the
  Metro Block.

  An Associated Press writer, photographer and cameraman interviewed and photographed the Metro Block fighters Tuesday in the village they're occupying
  on condition the locale not be named, nor any fighters identified by their full names.

  Some of the 1,200 Metro Block fighters - battle-hardened men who are responsible for executing dozens of suspected civilian rebel collaborators - said they
  did not look forward to fighting their former comrades-in-arms.

  "This could get ugly," said a fighter known as Eliecer, who used to work with Castano.

  Political analyst Alfredo Rangel said Castano gave the ultimatum to Rodrigo in order to reassert his leadership over paramilitary factions and gain more
  authority during peace talks.

  Rodrigo, the Metro Block commander, told the AP his men have every intention to continue fighting the rebels - and Castano's men if it comes to that.

  Castano has not publicly commented on the standoff.

  In January, President Alvaro Uribe named a government commission to contact Castano and other paramilitary leaders. The commission has since met with
  paramilitary leaders several times to discuss disarmament, but few details on progress of the talks have been released.

  One political analyst and expert on the paramilitary movement said the government should monitor the paramilitary feud and prevent yet another front
  from erupting in Colombia's war, now in its 39th year.

  "The government should pay attention to this ... because it will further weaken institutions, will surely affect civilians, and will eventually involve the armed
  forces," said Alvaro Jimenez, co-author of the book "The True Intentions of the Paramilitaries."

  Colombia's army commander, Gen. Carlos Ospina, has dismissed the feud as "a fight between bandits."