WASHINGTON- A key U.S. Senate committee endorsed a sweeping healthcare overhaul on Tuesday, gaining the support of an influential Republican and delivering President Barack Obama a victory on his top domestic priority.

The Democratic-controlled Senate Finance Committee approved the measure on a 14-9 vote, with Senator Olympia Snowe becoming the first Republican in Congress to back a healthcare reform bill.

Snowe, who had been courted by Obama and his fellow Democrats as the only potential Republican yes vote on the panel, said she backed the plan with reservations and she could not guarantee her continued support as the overhaul advances through Congress.

My vote today is my vote today. It doesn't forecast what my vote will be tomorrow, Snowe said.

Health insurer stocks extended their losses for the day after the news that Snowe would vote for the overhaul. The S&P Managed Health Care index of large health insurers was down 2.3 percent in afternoon trading.

The proposal to reduce costs, regulate the insurance market and expand coverage was the last of five pending health bills to clear a committee in Congress. It will be merged with the Senate health panel's version and moved to the full Senate for debate in the next few weeks.

Pretty much everything has been said and now it's time to get the job done, Democratic Chairman Max Baucus said in opening the committee meeting. Americans are looking for common-sense solutions.

Republicans condemned the plan as a costly and heavy-handed government intrusion into the private healthcare sector and said the measure would get even worse as it moves forward.

We can now see clearly that the bill continues its march leftward, said Senator Charles Grassley, the senior Republican on the panel. This bill is already moving on a slippery slope to more government control of healthcare.

Snowe's support could give Democrats a crucial swing vote as they try to hold the 60 Senate votes needed to overcome procedural roadblocks. Democrats control exactly 60 seats in the 100-member Senate.

Americans want us to craft a package that will get the 60 votes to pass, said Baucus, who led months of negotiations with three committee Republicans, including Snowe.

Two weeks of panel debate left the key elements of Baucus' plan intact. Support was strengthened by last week's estimate from nonpartisan analysts that it would cost $829 billion -- well below Obama's target of $900 billion -- and meet the president's goal of reducing the budget deficit. (Editing by Doina Chiacu)