WASHINGTON — The Senate, with Democrat Ted Kennedy casting a crucial vote, approved legislation by a veto-proof margin Wednesday that would void a 10.6 percent pay cut for doctors treating Medicare patients.

The bill now goes to the White House. The House already approved the measure, but a Senate vote two weeks ago fell one vote short of the 60 votes needed to limit debate. Kennedy, undergoing radiation and chemotherapy treatments for brain cancer, was not present then.

His presence Wednesday was instrumental as the vote to limit debate was approved 69-30. Under a previous agreement, once the 60-vote threshold was met, the bill was considered approved.

Nine Republicans voted for the measure after previously voting against limiting debate. President Bush’s advisers have said they will recommend that he veto the bill.

Lawmakers are under pressure from doctors and the elderly patients they serve to void the cut, which kicked in July 1 because of a funding formula that establishes lower reimbursement rates when Medicare spending levels exceed established targets. Some doctors say they’ll quit taking new patients if the cuts stand.

Medicare officials will not make any payments at the reduced rate until July 15 at the earliest.

Every year, Congress confronts the task of voiding Medicare rate cuts for doctors. Lawmakers always find it difficult because they make up the costs by trimming payments to other health care providers.

This year, Democrats homed in on cutting the Medicare Advantage program, which serves 9 million elderly and disabled patients. The Bush administration and Republicans like Medicare Advantage because it lets the elderly and disabled choose to get their health benefits through private insurers rather than through traditional Medicare. Democrats contend that government payments to the insurers are too generous.

If the bill becomes law, the Congressional Budget Office projected that insurers would get about $13.5 billion less over the next five years through Medicare.

Sen. Max Baucus, D-Mont., said the dynamics changed when the House voted 355-59 in favor of the bill. The bill would freeze payments to doctors this year and give them a 1.1 percent rate increase in 2009.

The nine Republicans who switched their votes from June 26 were: Sens. Lamar Alexander and Bob Corker of Tennessee, Saxby Chambliss and Johnny Isakson of Georgia, John Cornyn and Kay Bailey Hutchison of Texas, Mel Martinez of Florida, Arlen Specter of Pennsylvania and John Warner of Virginia.