Colombia's defence minister welcomed the comments - if they led to action
Colombia's defence minister has welcomed a call by Venezuelan President Hugo Chavez for Farc rebels to end their four-decade struggle.
Mr Chavez, whom Colombia has accused of financing Farc, had earlier said the group was "out of step" and called on them to release all their hostages.
Colombian Defence Minister Juan Manuel Santos welcomed the comments as long as they were "translated into action"
The US described Mr Chavez's statements as "good words".
"We would encourage Venezuela to follow those good words with concrete actions," State Department spokesman Sean McCormack said.
Colombian Defence Minister Juan Manuel Santos welcomed Mr Chavez's comments as long as they were "translated into action".
"Our fundamental strategic objective is that our neighbours collaborate in the fight against terrorism," said Mr Santos.
He said the move meant that Colombia and Venezuela would be able to renew their ties, to the benefit of both nations.
The Revolutionary Armed Forces of Colombia (Farc) hold many hostages, including about 40 high-profile captives they say they want to swap for imprisoned rebels.
The rebels are believed to be at their weakest point in years, following the death of their long-time leader, Manuel Marulanda, in March.
'Guerrilla war is history'
In his weekly television and radio programme on Sunday, the Venezuelan president said ending the rebellion could lead to a peace process between the rebels and the Colombian government.
Colombia has previously accused Hugo Chavez of funding Farc
"The guerrilla war is history," he said. "At this moment in Latin America, an armed guerrilla movement is out of place."
Colombian Interior minister Carlos Holguin said the statement from Mr Chavez was "surprising" as the Venezuelan leader had been "a great defender and ally of the guerrillas".
But Mr Holguin added: "It's great, and I hope Farc hears him."
BBC Americas editor Emilio San Pedro says the message represents an about-face for Mr Chavez, who a few months ago called on the world to regard Farc as a legitimate army rather than a terrorist group.
Our correspondent says Mr Chavez's critics will wonder whether this change is related to allegations by Colombia's President Alvaro Uribe - who accused Mr Chavez of giving the rebels $300m (£150m).
In March, Colombia said it had found documents on a computer that proved Venezuela funded Farc.
The computer was seized during a raid on a Farc camp in Ecuador, in which another senior Farc leader, Raul Reyes, was killed.
Venezuela said any contacts with Farc were solely made as part of a humanitarian effort to free hostages.
The captives include Franco-Colombian politician Ingrid Betancourt and three Americans.
Earlier this year Mr Chavez negotiated the release of two key hostages, Clara Rojas and Consuelo Gonzalez.
Late last year his official mediation role was terminated by Mr Uribe, who said Mr Chavez had overstepped his responsibilities.
Farc is the oldest and largest group among Colombia's left-wing rebels - and is one of the world's richest guerrilla armies.
It was founded in 1964 when it declared its intention to use armed struggle to overthrow the government and install a Marxist regime.
But like most of the paramilitary groups in Colombia's 40-year civil conflict, it has become increasingly involved in the drug trade.
Colombia is known as the "kidnap capital of the world", with one person a day, down from 10 a day in 2002, being snatched either for ransom or political bargaining.