The US Senate, torn along party lines, voted to formally launch debate on historic legislation to enact President Barack Obama's signature drive to remake US health care, handing him a win for now.

The 100-seat chamber's two independents joined all 58 Democrats -- including two waverers who declared their intentions just hours earlier -- to launch what is expected to be a weeks-long fight over opposition from 39 of 40 Republicans.

Republican Senator George Voinovich of Ohio did not vote.

"The President is gratified that the Senate has acted to begin consideration of health insurance reform legislation," White House spokesman Robert Gibbs said.

"Tonight's historic vote brings us one step closer to ending insurance company abuses, reining in spiraling health care costs, providing stability and security to those with health insurance, and extending quality health coverage to those who lack it. The President looks forward to a thorough and productive debate," Gibbs added.

The measure -- which includes a government-backed insurance program to compete with private firms and restrictions on dropping care for pre-existing ailments -- is estimated to cost 848 billion dollars through 2019 but cut the sky-high US budget deficit by 130 billion dollars over the same period.

A successful final vote -- expected a month away at the earliest -- would force the Senate and the House of Representatives to reconcile their rival versions of the bill and vote again to send it to Obama.

Republicans, one of whom has vowed a "holy war" against the bill, hope to kill the bill or delay the battle into next year with the expectation that the 2010 midterm elections may make it harder for centrist Democrats to support it.