U.S. Sen. Ron Wyden of Oregon has prostate cancer and will miss late-session votes that could include approval of an arms treaty with Russia and repeal of the "don't ask, don't tell" law on gays in the military, he said Thursday.

The 61-year-old Democrat said the cancer is in its early stage, diagnosed after his annual physical examination in late November. He said he scheduled surgery for Monday at Johns Hopkins Hospital, expecting the Senate to be in recess by then.

"However, it now appears that I will be missing votes tomorrow and possibly next week," he said in a statement.

Wyden has surgery preparation scheduled Friday but would be available for votes on the weekend, said a spokeswoman, Jennifer Hoelzer.

On the congressional agenda are a government appropriations bill, a new arms treaty with Russia and legislation to allow openly gay servicemembers to remain in the military, but aides said the schedule is so fluid it's not certain what votes Wyden would miss.

Regan Lachapelle, a spokeswoman for Senate Majority Leader Harry Reid, said time is too short for the Senate to adjust its schedule to make sure Wyden is on the floor for critical votes, and it's not clear that his votes would be make-or-break for measures such as the repeal of the "don't ask, don't tell" policy or the arms treaty.

"We expect all those votes to be close," she said.

Wyden would vote for both measures, said spokesman Tom Caiazza.

Wyden has been a durable figure in Oregon politics, first as an advocate for the elderly in the 1970s and then as a member of Congress for three decades. His legislative interests range from health care and financial reform to the environment and jobs. Despite solid liberal credentials, he also has a reputation for working across party and interest lines.

Last month, he was re-elected handily to the Senate seat he's held since 1996. Before that, he served eight terms in the House, beginning in 1980.

Wyden said one in six men will be diagnosed with prostate cancer, and early detection through routine physicals "is critical to catching this disease when treatment is most effective." He said he expected to make "a full and speedy recovery."

He could be out of the hospital as soon as Tuesday, and "after that we're going to play it by ear," Hoelzer said.

Wyden said he expects to be back at work full-time when the Senate reconvenes in January.