It also recently announced a halt to ransom kidnappings that have been a financing tool along with the cocaine trade.
Yet neither the insurgents, who have about 9,000 fighters, nor Colombia's armed forces have eased up on military operations.
The military's March 21 raid in Arauca came four days after rebels in the same region killed 11 soldiers in an attack.
Santos, who was defense minister in 2006-2009, said Monday that the armed forces "will not stop, will continue and will persevere" in their mission.
Military analyst Alfredo Rangel said the government's military offensive could prompt the FARC to delay the prisoner releases. Doing so, however, would badly "hurt its image before the nation and international community," he said.
An activist who has long worked for the freedom of security force members held by the FARC, and who is slated to receive the 10 captives, expressed optimism Monday.
"I don't think that because of these operations the releases will be canceled," said the activist, Marleny Orjuela.
Associated Press writers Cesar Garcia in Bogota, Colombia, and Frank Bajak in Lima, Peru, contributed to this report.