President Bush, making a brief statement to reporters in the Rose Garden, struck an optimistic tone that echoed how aides said Snow was feeling. Mr. Bush said he looked forward to the day when Snow returns to the White House.

"His attitide is one that he is not going to let this whip him," Mr. Bush said. "My attitude is that we need to pray for him."

Snow underwent surgery Monday to remove a small growth in his lower abdomen, a procedure he said last Friday was being done "out of an aggressive sense of caution" because he had colon cancer two years ago.

Doctors determined that the growth was cancerous, and found during the surgery, which was exploratory, that his cancer had metastasized, or spread, to his liver, Perino said.

On the floor of the House of Representatives, Congressman Roy Blunt, R-Mo., said, "I've known Tony, we've all known Tony, for a long time and my belief is if anybody has the stamina and the fortitude and the positive nature to deal with this challenge, he has it," Blunt, who has also battled cancer, said.

"We're wishing him well and frankly hope he is back to work soon, because we need him," Blunt said.