Democrats in the United States Senate say they have secured the votes needed to begin a debate on a landmark healthcare bill.
President Barack Obama has prioritised reform of the healthcare system and the bill is designed to secure coverage for millions of uninsured Americans.
Two Democratic senators whose support had been in doubt say they will now back the move, assuring the party the 60 votes needed to pass the measure.
All but one of the Senate's 40 Republicans voted against it.
The BBC reports it may be a procedural vote, but is a test of Democratic unity and of Mr Obama's ability to rally members of his party around his domestic agenda priorities to deliver on his campaign promises.
Senate Democrat leader Harry Reid's proposed $US849 billion bill would extend coverage to another 31 million people, or 94% of eligible citizens.
The legislation, outlined in a 2,000-page document, is said by Democratic aides to reduce deficits by $US127 billion over a decade and by as much as $US650 billion in the 10 years after that.
The 100-member chamber's 40 Republicans will unanimously vote against it, saying it is too expensive.
If the motion is approved, it will still take weeks before a final bill reaches Mr Obama's desk to be signed into law.