Colombia's Farc rebels say they may cancel the release of a high-ranking general and other hostages because of heavy military presence in the area where they are being held.
In a statement, the rebels complained of massive troop deployments in the northern province of Choco.
The government suspended peace talks it had been holding with the rebels in Cuba after Gen Alzate was captured.
The rebels said they had been planning to free the hostages on Tuesday.
Gen Alzate was captured along with two soldiers on 16 November.