WASHINGTON — Senate Republicans vowed Wednesday to use every available tactic to delay voting on the health care bill, as Majority Leader Harry Reid, D-Nev., scrambled to unify Democrats in support of the legislation.

As of Wednesday night, Sen. Ben Nelson, D-Neb., was the only known holdout of the 60-member caucus, unsatisfied with language in the $848 billion legislation related to abortion coverage. Democratic leaders offered to revise the bill with tighter new restrictions. Nelson, an abortion opponent, said he wasn’t sure the new wording went far enough.

Meanwhile, on the Senate floor, Republicans showed they were prepared to extend the health care debate as long as possible, with Sen. Tom Coburn, R-Okla., demanding that a Senate clerk read aloud a 767-page Democratic amendment.

The GOP bid was foiled about three hours later, when Sen. Bernard Sanders, I-Vt., the amendment’s liberal sponsor, withdrew his long-shot bid to create a Canadian-style, single-payer system. But Republicans are expected to make a similar move when Reid introduces the revised Senate bill, likely to top 2,000 pages, later this week.

“We ought to take and embrace this idea of transparency and responsibility that the American people can expect every one of us to have read this bill . . . and certify that we have an understanding for what we’re doing to health care in America,” Coburn said.

Democrats decried the maneuver and predicted the GOP stalling effort would fail. “The decision by the Senate Republican leadership today to have the Sanders amendment read clearly tells us what their strategy is,” said Senate Democratic Whip Dick Durbin, D-Ill., “It is to slow down or stop this bill at any cost.”

Durbin said the Dec. 25 deadline for final passage remained intact, provided Reid can lock down the 60 votes needed to overcome a Republican filibuster. “I think that we can get this done in time for each of us to be home for Christmas. That’s our goal,” Durbin said.

But Nelson told reporters Wednesday that he remains undecided on the health care bill and won’t vote for the package “until and unless the things I’ve put before them are handled.”

Nelson said he would review a new proposal that participants in the talks said would segregate public and private funds in the new insurance exchanges that the bill would create for individuals who do not have access to affordable employer coverage. Under the Senate bill, people with incomes below 400 percent of the federal poverty level would receive government subsidies to purchase plans over the exchanges.

Nelson, along with numerous anti-abortion groups, want an ironclad ban that would prevent any subsidies being used to purchase policies that include abortion coverage.

Sen. Barbara Boxer, D-Calif., a leader of the pro-choice faction of the Senate Democratic caucus, said she was hopeful that a compromise could be reached. “We’re looking for those words that will just keep the status quo in play,” Boxer said. “If we’re real, if we all mean what we say, I feel we can do it.”

Despite the focus on abortion, other issues remain unresolved, and Democrats continue to push for changes to the legislation. Three senators, including Joe Lieberman, I-Conn., and John Rockefeller, D-W. Va., announced Wednesday they would seek to significantly increase the authority of a new independent Medicare advisory board that the Obama administration views as critical to reining in health care costs.

The amendment would scrap deals cut to exempt hospitals and hospices from additional Medicare payment cuts over the next decade, make clear that doctors and medical device manufacturers could also face payment cuts, authorize the board to cut Medicare spending sooner and more deeply, and ensure that the board could continue to force Congress to make Medicare cuts years into the future.

The proposal is sure to infuriate both provider groups and organizations representing the elderly, though the senators also propose to expand the scope of the board so it could make recommendations to cut costs across the entire health industry, a change sought by AARP and other seniors’ groups.

But the White House and many Democrats view the commission as one of the few items in the bill able to drive down health care costs over the long term.

“One of the most important goals of health care reform is reducing the cost of health care,” Lieberman said, who has yet to endorse the Senate bill. “The Independent Medicare Advisory Board is one of our most effective tools to do just that.”

In related developments:

One in five Americans of working age lacked health insurance during the first half of this year as the recession took a toll on coverage, the Centers for Disease Control and Prevention said. From January through June, 21 percent of people ages 18 to 64 had no insurance, the highest share since 2003 and up a percentage point from a year earlier, the Atlanta-based agency said. Counting people of all ages, 45.4 million weren’t covered, the CDC said. That’s 15.1 percent of the total population, up from 14.7 percent a year earlier.

Democratic senators said they’ve been told the pharmaceutical industry will contribute billions of dollars more than it has previously promised for Obama’s health care overhaul, with the money being used to close a gap in Medicare drug coverage.