WASHINGTON: President Barack Obama's historic drive to remake US health care got a fresh boost Saturday as the second of three wavering Democrats said she would vote to take up the sweeping legislation.

During a rare weekend session, Democratic Senator Mary Landrieu of Louisiana announced that she would cast her ballot later in the day in favor of opening a formal debate on the bill.

"There are enough significant reforms and safeguards in this bill to move forward, but much more work needs to be done," said Landrieu.

But "my vote today to move forward on this important debate should in no way be construed by the supporters of this current framework as an indication as to how I might vote as this debate comes to an end," she stressed.

Her comments came one day after swing-vote Democratic Senator Ben Nelson of Nebraska said he would vote the same way, leaving Democratic Senator Blanche Lincoln of Arkansas the only one still publicly uncommitted.

The procedural vote on whether to start the formal debate on the bill was scheduled for 8:00 pm (0100 GMT Sunday).

While it was a critical test for Obama's top domestic priority, a "yes" vote does not commit a lawmaker to backing the legislation for final passage.