House Republicans advanced their Medicare (search) plan past sharp Democratic objections, defending their heavy reliance on the private sector to deliver a new prescription drug benefit.

The GOP bill, approved late Tuesday by the House Ways and Means Committee (search), would pay a share of seniors' drug bills, a goal of lawmakers in both parties. But Democrats complained that the House bill was too stingy and argued it would undermine the very nature of the health care program serving some 40 million elderly and disabled Americans.

But majority Republicans hung together, and their bill was approved on a largely party-line, 25-15 vote. Hours of partisan debate suggested another nasty fight was ahead when the bill arrives on the House floor. A final House vote is expected by July 4.

Before the bill gained committee approval Tuesday night, Republicans defeated several amendments aimed at limiting the role of private insurance companies in running Medicare and its new drug benefit. And they defeated a much more generous Democratic alternative, which would have covered a larger share of seniors' drug costs.

Throughout the debate, Republicans argued that they were trying to strengthen Medicare by allowing competition from private companies.

"We're not trying to blow the program up," insisted Rep. Bill Thomas (search), R-Calif., chairman of the Ways and Means Committee, defending his party and recounting improvements to Medicare in recent years. "We want to make sure that Medicare is sustainable for today's seniors, but just as well for tomorrow's."

A second House panel was set to consider the bill Wednesday, after GOP leaders reached agreement with conservatives who weren't pleased with the bill.

Debate also was under way in the Senate, where many Democrats said they were supporting the bill as a strong first step despite their concerns.

Under the House measure, seniors who receive their medical coverage in traditional Medicare would pay a premium of roughly $35 monthly for drug coverage, with a deductible of $250. Insurance would then cover 80 percent of costs from $251 to $2,000. There would be no coverage from $2,000 to $4,900 in drug costs. After that level, insurance would pay 100 percent of drug costs.

In addition, the measure includes subsides for lower-income seniors that would substantially defray their costs.

Under the Senate bill, seniors would have a $275 deductible. Insurance would then cover half their drug costs, from $276 to $4,500. There would be no coverage at all from $4,500 to $5,800. After that, insurance would pay 90 percent of the cost.

Senators were to begin considering amendments Wednesday, aiming to pass their bill by the end of next week. Despite Democratic support for the legislation, their amendments were meant to highlight its weaknesses.

At Ways and Means, just one Democrat, Rep. Earl Pomeroy of North Dakota, voted for the bill and no Republicans opposed it.

The panel voted to block the government from offering a drug benefit to compete alongside privately administered plans. Like other amendments offered by Democrats, it was defeated on a party-line vote.

Republicans also voted to retain a provision forcing the overall government-run Medicare program to compete with private plans by 2010. That means it could wind up costing seniors extra if they want to stay in traditional Medicare, where they can pick their own doctor.

Thomas argued that the competition is needed to shore up the program's finances, which grow shakier each year as baby boomers approach retirement. He and others hope private companies will help drive down costs of care. But New York Rep. Charles Rangel, the senior Democrat on the committee, said this provision would mean "the end of Medicare as we know it."

Democrats offered an alternative plan, which would offer more generous benefits — at a cost approaching $1 trillion over 10 years.

"It provides an adequate prescription drug benefit for seniors, and that costs money," said Rep. Pete Stark, D-Calif. Addressing his GOP colleagues, he said: "You always seem to have money when it comes to tax cuts."

The committee accepted an amendment that increased Medicare payments to rural health providers.

Separately, the House Energy and Commerce Committee also was debating the bill.

There, a group of conservatives have been pushing an alternative approach that calls for tax breaks for contributions to a debit card that would be used to buy medicine.

Rep. Joe Barton, R-Texas., said he and others in his group had won agreement to have a version of their proposal inserted into the legislation through 2006, when the Medicare drug benefit would take effect.