Landmark health-care legislation backed by U.S. President Barack Obama passed its sternest Senate test in Monday's pre-dawn hours, overcoming Republican delaying tactics on a 60-40 vote that all but assures its passage this week.

"Let's make history," said Democratic Sen. Tom Harkin shortly before the bill's supporters demonstrated their command of the Senate floor in an extraordinary holiday season showdown.

The bill would extend coverage to more than 30 million Americans who now lack it, while banning insurance company practices such as denial of benefits on the basis of pre-existing medical conditions.

The atmosphere was intensely partisan, but the outcome pre-ordained as senators cast their votes from their desks, a practice reserved for issues of particular importance.

Administration officials who have worked intensely on the issue watched from the visitor's gallery despite the hour. So, too, did Vicki Kennedy, the widow of Democratic Sen. Edward M. Kennedy, who championed health care across a Senate career that spanned more than 40 years.