U.S. Senator Craig Thomas, a conservative Republican from the northwestern state of Wyoming, died Monday evening at the age of 74 after a fight with leukemia.

His family says Thomas died at the National Naval Medical Center in Bethesda, Maryland, where he had undergone chemotherapy for acute myeloid leukemia, a cancer of the blood and bone marrow.

President Bush expressed sadness at the senator's death, saying, "He was a man of character and integrity known for his devotion to the values he shared with the people of Wyoming."

Wyoming's governor, a Democrat, will name a successor from a list of three candidates chosen by the state's Republican Party.

Some information for this report was provided by AFP, AP and Reuters.