President Barack Obama pushed fractious Senate Democrats on Tuesday to pass a broad healthcare overhaul and said he was cautiously optimistic they could iron out their differences to win the 60 votes needed.

Obama summoned all 60 members of the Senate Democratic caucus to the White House to tell them to end their bickering and find common ground on a bill that could save money and improve millions of lives.

We are on the precipice of an achievement that has eluded Congresses and presidents for generations, Obama, himself a former senator, told reporters after meeting with Senate Democrats.

What I told my former colleagues today is that we simply cannot allow differences over individual elements of this plan to prevent us from meeting our responsibility, he said. I'm feeling cautiously optimistic we can get this done.

Senator Joe Lieberman, who threatened earlier this week to join Republicans in blocking the bill, said he was nearly ready to back it if proposals for a new government-run insurance program and an expansion of the government's Medicare program for the elderly and disabled were dropped as he demanded.

The overhaul of the $2.5 trillion healthcare industry, Obama's top domestic priority, has been bogged down in the Senate amid disputes over costs, plans for the government-run insurance program and abortion.

Senate Democrats say they will appease Lieberman, an independent who caucuses with Democrats, by dumping the proposal to expand Medicare to allow people ages 55 to 64 to buy Medicare insurance, now available to Americans at age 65.

I'm getting toward that position where I can say what I've wanted to say all along, that I'm ready to vote for healthcare reform, Lieberman told reporters. We're heading in the right direction.

Lieberman backed an expansion of Medicare as recently as in a September interview. But he said the provision was unnecessary in the Senate bill, which includes generous subsidies to help the uninsured buy coverage.

COMPROMISE ENDANGERED

The Medicare plan was part of a Democratic compromise to erase objections by moderates to a new government-run insurance program, known as the public option, which supporters said would create competition for private insurers but critics said would amount to a government takeover.

The compromise also replaces the public option with a non-profit coverage plan offered by private insurers and overseen by a federal agency. That proposal is expected to remain in the bill.

The decisions to drop the public option and the Medicare expansion angered some liberals. Former Democratic Party chairman Howard Dean said the Senate bill should be scrapped and the process started over.

This is essentially the collapse of healthcare reform in the United States Senate, he told Vermont Public Radio of the decision to drop the Medicare expansion.

But many Senate liberals said they were willing to dump the programs to pass a bill that would extend coverage to 30 million uninsured Americans and halt practices like refusing coverage to people with pre-existing medical conditions.

These are hard decisions in hard times that have huge consequences for the good, said Democratic Senator John Rockefeller, a strong backer of the public option.

Democrats have no margin for error on the healthcare bill. They control 60 of the 100 votes in the Senate -- exactly the number needed to overcome Republican procedural hurdles -- making each of their members a potential kingmaker.

Several other Senate Democrats -- including another potential defector Ben Nelson, who is seeking tougher language restricting abortion coverage -- are waiting for cost estimates on last week's compromise plan before making final decisions.

Those estimates, from the non-partisan Congressional Budget Office, could be released on Wednesday.

The Senate rejected an amendment to allow people to buy cheaper medication from other countries -- a provision that would have threatened a White House deal with drug makers, who had agreed to pay $80 billion over 10 years to help fund the health overhaul.

The United States spends more on healthcare than any other country. Healthcare costs devour 16 percent of the U.S. economy -- burdening states and the federal government while also hurting the competitiveness of U.S. businesses.

Obama has pushed the Senate to finish the healthcare bill this year to keep the issue from slipping into next year's congressional election campaigns.

The Senate bill would then be reconciled in early January with a version approved by the House of Representatives on November 7, a process House Democratic leader Steny Hoyer said will take some time. Each chamber would have to pass the bill again before sending it to Obama.

To finish in the Senate by Christmas, Reid must file a series of procedural motions in the next few days to cut off debate and move to a final series of votes.

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