Actor Michael Landon, star of "Bonanza," "Little House on the Prairie" and "Highway to Heaven," has inoperable cancer but vows "he's going to beat this," his spokesman said Monday.

"It is serious, obviously. But the doctor has not said it is a total loss or anything," said publicist Harry Flynn.Landon, 54, began have serious stomach pains about six weeks ago, Flynn said. The actor returned early from a Utah ski trip and entered Cedars-Sinai Medical Center in Los Angeles on Thursday for tests. The actor, secluded at his 10-acre Malibu estate, learned of his results Friday.

"He has cancer. It is in the liver and pancreas. We are all a little numb right now," Flynn said. "But as serious as it is, he is very positive. He said he's going to beat this."

Landon was recently informed that his fourth TV series, "US," in which he plays a traveling columnist, had been selected by CBS for its fall lineup.

Landon, who has nine children, and his third wife, Cindy, 34, live with their younger children on the Malibu ranch. "He's got a little weight loss, but he looks great," said Flynn.