BOGOTA (Reuters) - Colombia’s Marxist ELN rebels must free all 19 hostages it holds before President Ivan Duque, who is evaluating peace talks with the group, will resume dialogue, a senior government official said on Friday.

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The National Liberation Army (ELN) was in negotiations with the administration of former President Juan Manuel Santos since February 2017.

The last round of talks being held in Cuba between the Colombian government and ELN ended on Aug. 1. Duque, who took office on Aug. 7, said the group must end all violence and criminal activity for continuation of negotiations.

Miguel Ceballos, the government’s high commissioner for peace, said in an interview that “all those kidnapped - not just the nine kidnapped last month - must be released, and it must be immediate.” He said one captive has been held since 2002. He said the deadline to release them would end in a week.

Right-wing Duque said in his inaugural speech that he would review the negotiations and make a decision within 30 days.

The ELN, founded by radical Catholic priests, is considered a terrorist group by the United States and European Union. It has waged a five-decade war against the government, engaging in bombings, kidnappings, extortion and sabotage of oil pipelines.

“Their will is not clear yet, but we can sit down and talk and ask them if they really ... are thinking about laying down their weapons and joining society,” Ceballos said.

The ELN said in a tweet on Friday, “The ELN confirms its willingness to dialogue ... We continue in Cuba waiting for government delegation.”

More than 260,000 people have died in Colombia’s conflict including government troops and members of the ELN, the FARC and right-wing paramilitaries.

Santos was awarded a Nobel Peace Prize for his efforts to reach a peace agreement with the larger rebel group, the Revolutionary Armed Forces of Colombia (FARC), which is now a political party with seats in congress.

Duque has criticized that agreement, saying it was too lenient on the rebels.

During a ceasefire from September 2017 to January 2018, the ELN suspended hostage-taking, attacks on oil installations, the use of landmines and the recruitment of minors.