Washington (CNN) -- The AARP will endorse the House Democratic leadership's bill to overhaul health care, according to a Democratic source with direct knowledge of the plan.

The move comes as House Speaker Nancy Pelosi oversees final changes to the $1.1 trillion health care bill, which is likely set to come to a final vote Saturday.

The AARP is a nonprofit, nonpartisan group that advocates for people 50 and older.

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.

Meanwhile, the powerful American Medical Association also is set to weigh in on the debate, announcing its position on the House health care bill at a noon news conference.

A day after unveiling their $60 billion bill, House Republicans will hold an opposition rally on Capitol Hill. GOP leaders will join 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 severely 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.

House Democrats have rejected Republican overhaul plans 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 coverage for pre-existing conditions.

Pelosi's bill would extend insurance coverage to 36 million uncovered Americans and guarantee that 96 percent of Americans have coverage, according to the Democratic leadership.

The claim is based on an analysis by the nonpartisan Congressional Budget Office.

Among other things, the bill would subsidize insurance for poorer Americans and create health insurance exchanges to make it easier for small groups and individuals to purchase coverage. It also would cap annual out-of-pocket expenses and prevent insurance companies from denying coverage for pre-existing conditions.

Pelosi's office has said the bill would cut the federal deficit by roughly $30 billion over the next decade. The measure is financed through a combination of a tax surcharge on wealthy Americans and spending constraints in Medicare and Medicaid.

Specifically, individuals with annual incomes more than $500,000 -- as well as families earning more than $1 million -- would face a 5.4 percent income tax surcharge. Growth in Medicare expenditures would be cut by 1.3 percent annually.

The House bill also includes a government-run public option. Under the House plan, health care providers would be allowed to negotiate reimbursement rates with the federal government. Pelosi and other liberal Democrats had argued for a more "robust" public option that would tie reimbursement rates for providers and hospitals to Medicare rates plus a 5 percent increase. Several Democrats representing rural areas, however, killed the proposal after complaining that doctors and hospitals in their districts would be shortchanged under such a formula.

The House bill differs from legislation now being considered by the Senate in a number of critical ways. Senate Majority Leader Harry Reid, D-Nevada, also favors a public option but would allow individual states to opt out of the plan.

A bill recently passed by the Senate Finance Committee does not include a tax surcharge on the wealthy but would impose a new tax on high-end health care policies, dubbed "Cadillac" plans by critics. A large number of House Democrats are adamantly opposed to taxing such policies, arguing that such a move would hurt union members who traded higher salaries for more generous benefits.

Reid refused Tuesday to predict when the chamber would pass a health care bill, possibly signaling difficulty in generating support from his entire Democratic caucus.

President Obama has said he wants to sign a health care bill this year. However, Reid declined to offer a timetable when asked at a news conference if he believed the Senate would pass the bill by the end of December.

CNN's Dana Bash contributed to this report.