June 9 (Bloomberg) -- Colombia's military said its troops came close enough to three U.S. hostages held by guerrillas to hear them speaking in English, another sign government forces are closing in on the nation's biggest rebel group.

Units operating in the southeast province of Guaviare saw the three Americans bathing in the Apaporis River and listened to their conversation, Defense Minister Juan Manuel Santos said. Keith Stansell, Thomas Howes and Marc Gonsalves, employees of Northrop Grumman Corp., were kidnapped after their single-engine plane crashed on a drug surveillance mission in February 2003.

``We have had very accurate information about the location of the FARC leaders, the hostages and the camps,'' Santos said in an interview today with RCN Radio. He said surveillance was unable to determine whether former presidential candidate Ingrid Betancourt was with them.

The sighting, the second time in seven months proof has surfaced the Americans are still alive, underscores how the Colombian military has ramped up its intelligence on the Revolutionary Armed Forces of Colombia, or FARC. A growing number of defectors is helping the government increase pressure on the remaining fighters, disrupting the FARC's financing and supply lines, and leading to the capture or killing of top- echelon leaders, Santos said.

Venezuelan Arrests

Colombian forces on June 7 arrested four men including a member of Venezuela's National Guard, who were allegedly selling as many as 40,000 rounds of ammunition for AK-47 assault rifles, the most-common weapon of the FARC, according to Colombia's Attorney General Mario Iguaran.

Venezuela Interior Minister Ramon Rodriguez Chacin said today on state television the guard was ``tricked'' into crossing the border and then handed the ammunition.

The arrests were tied to the same-day capture of a security chief for Jorge Briceno, known as ``Mono Jojoy,'' the FARC's top military commander and member of the FARC's seven-member leadership, Iguaran said.

Mono Jojoy, a diabetic, is in poor health as the drugs and foods he needs can't reach his jungle hideout, according to the government.

`Guerrilla War'

The guerrillas, who hold as many as 750 hostages for ransom and political bargaining chips, are cornered in the country's most remote regions with their ranks reduced to as few as 8,000 fighters from as many as 17,000 before President Alvaro Uribe took office in 2002. At that time, guerrilla attacks and bombings were common inside Bogota and other major cities.

International pressure on the FARC to free its hostages took an unexpected turn yesterday when Venezuelan president Hugo Chavez urged the rebels to give up their armed struggle and unilaterally release all their captives, some of whom have been held for more than 10 years.

``Guerrilla war has passed into history,'' Chavez said in his regular Sunday television program, ``Alo, Presidente.'' ``You in the FARC should know, you have become an excuse, an excuse for the empire to threaten all of us.''

Chavez, on Jan. 11, called the FARC, designated a terrorist group by the U.S., Canada and the European Union, a real army with legitimate political goals, worthy of the world's respect. Colombia accuses the Venezuelan president of assisting the rebels with arms and as much as $300 million in financing.

U.S.

Computers retrieved after a Colombian raid into Ecuador on March 1 killed the FARC's second-in-command Raul Reyes revealed ties between Chavez, Ecuador's President Rafael Correa and the guerrillas, according to Colombian officials. Both leaders have denied links to the group.

Chavez's comments were welcomed today as ``good words'' by the U.S.

``The Venezuelan government should make every effort, public and private, to distance itself from any relationship it may have had with the FARC,'' U.S. State Department spokesman Sean McCormack told reporters in Washington.

Other blows to the FARC include the death of Manuel Marulanda, the group's founder, who died in March of a heart attack as the military launched a bombing operation near his camp, according to the government.

Offers of cash and amnesty have prompted desertions by key rebels such as the bodyguards of Ivan Rios, a member of the guerrillas' six-member high command. Rios's security team killed him and delivered his severed right hand and computer to Colombian authorities on March 7.

Out of Food

On May 19, the FARC's highest-ranking female commander, Nelly Avila Moreno, alias Karina, surrendered. She said in a news conference she was tired of fighting and that her unit, the 47th Front, was surrounded and running out of food. Moreno, considered one of the most dangerous FARC commanders after being involved in several massacres, according to El Tiempo newspaper, had been part of the FARC's 44-year war against the government for most of her life.

Colombian officials in November obtained the first images in four years that revealed the three contractors and Betancourt are alive. The footage showed the men staring blankly at the FARC camaras, while Betancourt was chained and looked thin and downcast.

To contact the reporter on this story: Helen Murphy in Bogota at Hmurphy1@bloomberg.net.

Last Updated: June 9, 2008 18:09 EDT