That dire view was reinforced last week when Cuba's foreign minister backed away from his prediction the ailing Castro would return to power by early December. "It's a subject on which I don't want to speculate," Felipe Perez Roque told The Associated Press in Havana. US government officials say there is still some mystery about Castro's diagnosis, his treatment and how he is responding. But these officials believe the 80-year-old leader has cancer of the stomach, colon or pancreas. He was seen weakened and thinner in official state photos released late last month, and it is considered unlikely that he will return to power or survive through the end of next year, said the US government and defense officials. They spoke on condition of anonymity because they were not authorized to speak publicly about the politically sensitive topic. With chemotherapy, Castro may live up to 18 months, said the defense official. Without it, expected survival would drop to three months to eight months. American officials will not talk publicly about how they glean clues to Castro's health. But US spy agencies include physicians who study pictures, video, public statements and other information coming out of Cuba. A planned celebration of Castro's 80th birthday next month is expected to draw international attention. The Cuban leader had planned to attend the public event, which already had been postponed once from his Aug. 13 birthday.