WASHINGTON – Buoyed by two major endorsements, House Democratic leaders on Thursday predicted swift passage of President Barack Obama’s historic health overhaul initiative. The president himself declared, “We are closer to passing this reform than ever before.”

With a vote set for Saturday, momentum gathered behind the sweeping legislation to remake the U.S. health care system and extend coverage to millions of the uninsured. The American Medical Association and the powerful seniors’ lobby AARP both threw their weight behind the bill Thursday. AARP, with its 40 million members, promised to run ads and contact activists to gin up support.

“I urge Congress to listen to AARP, listen to the AMA, and pass this reform for hundreds of millions of Americans who will benefit from it,” Obama told reporters during an unannounced visit to the White House briefing room after the endorsements were announced.

At the other end of Pennsylvania Avenue, Democrats were listening.

“We are right on the brink,” said House Speaker Nancy Pelosi. “We have an historic opportunity for us to again provide quality health care for all Americans. It is something that many of us have worked our whole political lifetimes on.”

Pelosi and other Democratic leaders were working to negotiate final language on abortion and illegal immigration and nail down the 218 votes they’ll need to pass the bill. Obama planned to give them an assist today with a rare visit to Capitol Hill to shore up any wavering support.

Despite the optimism, work remained to be done, and a much slower timeline in the Senate made the outcome unpredictable. Action in the Senate may not come until next year, and legislation passed by the two chambers would have to be reconciled before a bill could go to Obama.