Sen. John W. Warner was hospitalized for the third time in a month Wednesday for what his office called a "low-grade infection" related to his treatment for a minor heart problem.

Doctors discovered an infection in the 80-year-old senator's thigh during a follow-up appointment at Inova Fairfax Hospital, according to a statement from Warner's office.

He was admitted to the hospital for treatment and observation and should be able to return to the Senate next week, the release said.

Warner, a Republican, announced in August he would not seek a sixth term next year. Democratic former Gov. Mark R. Warner has already announced plans to run for the office, and another former governor, Republican Jim Gilmore, is likely to announce later this year whether he will run.

The Warners are not related.

The senator was hospitalized on Oct. 2 for two days while doctors performed a common non-surgical procedure for cardiac arrhythmia. For years, Warner had experienced minor bouts of the problem, which is not unusual and not necessarily life threatening if medically treated.

On Oct. 16, however, he was readmitted so surgeons could repair what his office described as a small aperture in an artery in the senator's thigh related to his treatment two weeks earlier.

At Wednesday's follow-up, doctors found an infection on the same spot on his thigh. They expect Warner recover fully from the infection, according to the statement from his office.

"We're going to make sure this is taken care of," Warner's spokesman, Carter Cornick, said in an interview with the Associated Press. "It is the case that where you've got surgery, you've got a substantial risk of infection, and we drew the short stick on this one."

In announcing his plans to retire from politics Aug. 30 at the University of Virginia, Warner said his health was excellent and did not factor into his decision.

After his release from the hospital on Oct. 4, Warner conducted a round of telephone interviews with reporters and, in a strong voice, said doctors told him his heart was healthy.

"I've got the heart of a 40-year-old," he boasted.

His departure from the Senate opens a seat Democrats believe they can win next year in Virginia and possibly expand their one-seat Senate majority with the popular and wealthy Mark Warner in the race.

Democratic newcomer Jim Webb upset Republican Sen. George Allen last fall. If Mark Warner wins next year's Senate race, it would be the first time since 1970 that Democrats have controlled both Senate seats in Republican-leaning Virginia.

Republicans will choose their nominee at a statewide convention in June. Besides Gilmore, U.S. Rep. Thomas M. Davis, a moderate who represents a suburban Washington, D.C., district, has also expressed an interest in running, but announced last week he would not be a candidate.

John Warner has said at least twice that he wanted to see a Republican with congressional experience seek the seat. Besides Gilmore, an anti-tax conservative, no other Republican has voiced an interest in running.