The United States has welcomed statements by Venezuelan president Hugo Chavez urging Colombian rebels to free hostages, but Washington said Caracas should also distance itself from the rebel group.
Colombia accuses the anti-US Chavez of supporting the rebels, known as the Revolutionary Armed Forces of Colombia, or Farc. But on Sunday he urged them to release unconditionally all prisoners from jungle camps, saying Colombia's decades-old civil war was anachronistic.
"Those are certainly good words," State Department spokesman Sean McCormack told reporters. "And we would encourage Venezuela to follow those good words with concrete actions."
"The Venezuelan government should make every effort, public and private, to distance itself from any relationship it may have had with the Farc," McCormack said.
Chavez is under pressure over his ties with Farc after Interpol confirmed the authenticity of some rebel computer files. Columbian and US officials have said the files show close cooperation between the guerrillas and the Chavez government.
Chavez denies the charges and says his goal is to negotiate an end to Colombia's civil war. He said on Sunday the conflict was serving as an excuse for the United States to use its military aid in the region and treat him as an enemy.
McCormack said he believed everybody in the region "would like to see Venezuela take concrete actions to put to rest any idea, whether in theory or in fact, that there is a relationship between - an ongoing relationship between the Farc and Venezuela."
Farc holds hundreds of captured security forces in secret camps as well as dozens of hostages it hopes to swap for its own senior imprisoned rebels.
Chavez mediated the first major hostage releases in years in January and February but there has been no further progress toward freeing more prisoners.