Washington (CNN) -- The push to overhaul health care received a major boost Thursday as the American Medical Association and AARP endorsed legislation drafted by top House Democrats.



The AARP, the nation's largest organization of older Americans, is a nonpartisan group that advocates for people 50 and older. The AMA, historically an opponent of health care reform, is considered one the nation's most influential doctors' advocacy groups.



"I want to thank both organizations again for their support, and 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," President Obama said at the White House.



The backing of those two groups comes as House Speaker Nancy Pelosi, D-California, oversees final changes to the $1.1 trillion health care bill. The measure likely will come to a final vote Saturday.



Read the House health care bill (PDF)



A 42-page manager's amendment on the health care legislation posted Tuesday night made mostly technical changes in the nearly 2,000-page bill compiled from three Democratic proposals passed by three House committees.



By making the changes public Tuesday, House Democratic leaders could open floor debate on the bill Friday, while fulfilling their pledge to allow 72 hours of review before bringing the measure to the full chamber.



Pelosi insisted Thursday she will have the 218 votes necessary to pass the bill. Meanwhile, President Obama is set to huddle Saturday with congressional Democrats on Capitol Hill to review the legislation.



Check out the key parts of the bill



In a statement, AARP CEO Barry Rand said, "We started this debate more than two years ago with the twin goals of making coverage affordable to our younger members and protecting Medicare for seniors.



"We can say with confidence that [the House bill] meets those goals with improved benefits for people in Medicare and needed health insurance market reforms to help ensure every American can purchase affordable health coverage."



The AMA's president, Dr. J. James Rohack, told reporters Thursday that the legislation is "not a perfect representation of our views" but is close enough to warrant his group's support and keep the reform process moving forward.



Rohack said the bill needs to be accompanied by legislation reversing scheduled Medicare reimbursement payment reductions to physicians.



Responding to the AMA endorsement, Obama said the doctors' group is "supporting reform because [its members have] seen firsthand what's broken about our health care system," Obama said.



"They would not be supporting it if they really believed that it would lead to government bureaucrats making decisions that are best left to doctors."



Watch Obama say health care reform is moving forward



Meanwhile, House Republicans on Thursday continued to signal their opposition to the measure. GOP leaders held a rally on Capitol Hill along with "Tea Party" movement protesters and other activists to warn that the House legislation would translate into a full-blown government takeover of the health care system.



Rep. Michele Bachmann, R-Minnesota, told CNN's "American Morning" on Thursday that Democrats had forgotten the lessons of August's town hall meetings when angry conservatives criticized health care legislation.



"I think what we're going to see is the town hall coming to Washington, D.C., just to remind members of Congress [that] we're the ones we would like you to pay attention to, not lobbyists. And we don't want the government to own our health care," Bachmann said.



Speaking at Thursday's opposition rally, actor John Ratzenberger, who played Cliff on the sitcom "Cheers," slammed the Democratic bill as a form of socialism.



"These are Woodstock Democrats," Ratzenberger said. "We have to remember where their philosophy comes. It doesn't come from America. It comes from overseas. It comes from socialism. And socialism is a philosophy of failure."



House Democrats have rejected an alternative $60 billion Republican plan as inadequate for meeting the goals of expanding health coverage to most of the nation's 46 million uninsured while bringing down costs and ending controversial industry practices such as denying
Where are the Tea Party protesters holding a rally? Who does Obama praise? Who is Nancy Pelosi? What association did Obama praise? How many votes were needed to pass the house bill? How many votes are needed to pass the House bill?
Capitol Hill AMA House Speaker Medical 218 218
question: Where are the Tea Party protesters holding a rally?, answer: Capitol Hill | question: Who does Obama praise?, answer: AMA | question: Who is Nancy Pelosi?, answer: House Speaker | question: What association did Obama praise?, answer: Medical | question: How many votes were needed to pass the house bill?, answer: 218 | question: How many votes are needed to pass the House bill?, answer: 218