Right-wing paramilitaries in Colombia have suspended their demobilisation in a dispute over the possible extradition of a commander to the US.
The US suspects Don Berna of involvement in drugs trafficking
The move was prompted by the transfer of Diego Fernando Murillo, known as Don Berna, from house arrest to prison.
The paramilitaries are due to disarm by the end of the year as part of a peace process - but leaders said they feared their legal position was now unclear.
The government has yet to respond to the announcement by the paramilitaries.
The US alleges that Don Berna worked for the drug-trafficker Pablo Escobar before emerging as a commander in the United Self Defence Forces of Colombia (AUC).
He was moved to a maximum-security prison north of the capital, Bogota, last week in response to pressure from the US.
The Colombian government has said Don Berna will not be extradited provided he honours the terms of a peace process with the government.
But the right-wing paramilitaries have said his transfer to prison has dented their faith in the deal.
"The demobilisation timetable is suspended as of now until the government makes the rules of the game clear and offers the necessary guarantees to restore confidence," AUC political chief Ivan Roberto Duque said.
Some 11,000 paramilitaries have already laid down arms in return for a government amnesty. Under the terms of the controversial two-year peace process, those who have committed crimes face reduced prison terms.
The government hopes that by the end of the year, all 19,000 members of the AUC will have disarmed.
Tens of thousands of civilians are known to have died during Colombia's 40-year civil conflict, involving left-wing rebels, right-wing paramilitaries and state forces.