The U.S. believes Fidel Castro's health is failing and he probably won't make it through 2007.

U.S. government officials say there is still some mystery about what ails the 80-year-old Cuban dictator, but they believe he has either stomach, colon or pancreatic cancer.

The Castro government has denied those claims in recent months, maintaining that Castro would be back at work by early December. However, one official backed away from those statements on Sunday.

"It's a subject on which I don't want to speculate," Foreign Minister Felipe Perez Roque told The Associated Press in Havana.

In state photos released this month, Castro appeared weaker and thinner than in the past. U.S. defence and government officials, speaking on the condition of anonymity, said it is considered unlikely that Castro will return to power or live past next year.

If the U.S. diagnosis is correct, Castro could possibly live up to 18 months, the defence official told AP. Without that treatment, however, his life expectancy could drop to three to eight months.

Though their methods for collecting medical information on Castro are top secret, U.S. spy agencies include physicians who study photographs, video, public statements and any other information available, to come up with their diagnosis.

Castro has planned to attend his own 80th birthday party next month. The celebration was postponed from his actual birthday, which is on Aug. 13.

With files from The Associated Press