As negotiations to end Colombia’s half-century conflict close in on a final deal, attention is turning to the fate of an aging bank manager turned leftist rebel who is being held at a U.S. maximum security prison alongside notorious terrorists.

The Revolutionary Armed Forces of Colombia consider Ricardo Palmera to be a prisoner of war and have long insisted he be released for a peace accord to be signed. But the administration of U.S. President Barack Obama has long rejected freeing Palmera, who is serving a 60-year sentence in connection to the FARC’s holding captive of three American defense contractors for more than five years a decade ago.