President Barack Obama planned to host his Democratic Senate allies Tuesday in a bid to rescue his embattled campaign to remake US health care, still looking to pass the legislation by Christmas.

Obama invited all 58 Senate Democrats and two independents who often side with them in a quest for the 60 votes needed to ensure passage of what would be the most sweeping overhaul of its kind in four decades.

Ahead of the high-stakes meeting, Vice President Joe Biden warned any Democratic lawmakers resisting even a watered-down compromise approach that they risked Obama's wrath if the historic legislation goes down to defeat.

Resisting Democrats won't "have a friend in the Lord"

"If they don't fear him, (they) are underestimating the steel in this guy's spine. This, to him, is the single most important thing to get done now," Biden said on the MSNBC television network.

Remaking US health care will be "kicked back for a generation" if it fails now, and any Democrat who "for their own shallow purposes" helps scuttle it "is not going to have a friend in the Lord," Biden said, using an expression from his home state of Delaware.

He spoke a day after Independent Senator Joseph Lieberman upset Democrats by signaling he would oppose expanding the Medicare program for the elderly and disabled, a key part of a behind-the-scenes compromise to win over a handful of swing-vote centrist lawmakers.

"I'm confident that Joe is going to see the light. I'm confident that Joe is going to vote for a final bill here. But there's an awful lot of gamesmanship going on right now," said Biden.

Lawmakers from the party's left flank, already angry over decisions to drop a government-backed "public option" health plan and tighten restrictions on abortion to appeal to centrists like Lieberman, were likely to be furious.

Lieberman, who campaigned for Obama's Republican White House rival in 2008, Senator John McCain, said he opposed allowing aged 55-64 to "buy in" to Medicare, despite backing that kind of plan just months ago.

Biden suggested that some centrists publicly signaling they could doom the measure were looking to wring concessions from Democratic Senate Majority Leader Harry Reid.

Looking for maximum leverage

"Everybody figures their maximum point of leverage is right before the deal's made. So, you've got everybody lining up out there, saying, 'if I just am willing to hold out now, I'll get everything I want,'" said Biden.

"We have gone over most of the hurdles," Reid said. "I'm confident that by next week we'll be on our way to forward this bill to the president."

The Senate and House of Representatives ? which has already approved its version of the legislation ? must pass the same bill to send it to Obama to sign into law.

The president was to meet with the lawmakers, including Lieberman, at 1.40pm (1830 GMT ,or 8.30pm South African time), and make a public statement afterwards.

The White House-backed bill aims to extend coverage to some 31 million Americans out of the roughly 36 million who currently lack it, while curbing soaring costs and improving the quality of care.

The United States is the world's richest nation but the only industrialized democracy that does not provide health care coverage to all of its citizens, about 36 million of whom are uninsured.

Washington spends more than double what Britain, France and Germany do per person on health care, but lags behind other countries in life expectancy and infant mortality, according to the Organization for Economic Cooperation and Development (OECD).