Associated Press - November 21, 2009 12:05 PM ET

WASHINGTON (AP) - Democratic senators are pressing toward a crucial first vote on President Barack Obama's health care overhaul on Saturday night.

The vote will be a test of party unity in the face of solid Republican opposition.

Democratic leaders are optimistic of success, but two moderate Democrats remained uncommitted. The vote is expected around 8 p.m. Eastern.

Centrist Democrat Ben Nelson of Nebraska announced Friday that he'd support his party on the debate vote, but he cautioned that doesn't mean he'll support the health care bill.

The vote will determine whether debate can go forward on the bill to dramatically remake the U.S. health care system over the next decade.

The bill would require most everyone to purchase insurance, and billions in new taxes would be levied on insurers and high-income Americans. Insurance companies would no longer be allowed to deny coverage to people with medical conditions or drop coverage when someone gets sick.

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