Two of the Senate's most liberal lawmakers are assailing a $6.3 billion medical research bill as a gift to drug companies, even as Republican leaders prepare to try pushing the measure through the lame-duck Congress.

"It's time for Congress to stand up to the world's biggest pharmaceutical companies, not give them more handouts," Sen. Bernie Sanders, I-Vt., said Tuesday in a written statement.

The comments by Sanders came a day after Sen. Elizabeth Warren, D-Mass., delivered a ferocious attack on congressional Republicans and Senate Majority Leader Mitch McConnell over the legislation and pushed fellow Democrats to oppose a measure she said "is corrupt, and it is very, very dangerous."

The opposition by Sanders and Warren was noteworthy because it comes as progressives and moderates are struggling over the direction the Democratic Party should take in the wake of its defeats on Election Day. Hillary Clinton lost her White House bid to Republican Donald Trump and Democrats remained in the House and Senate minority, making only small gains in each chamber.

In remarks Tuesday to the Senate, Minority Leader Harry Reid, D-Nev., said there is "some angst" among Democrats about the bill and that he was expecting it to be changed, but he was not specific.

The House planned to consider the 996-page measure on Wednesday, and Senate debate was expected next week, which is likely to be the final week of this year's postelection Congress.

The bill would let the Food and Drug Administration approve drugs and medical devices more quickly and bolster federal mental health programs. It lays plans for $4.8 billion in additional spending over the next decade for cancer, brain and other biomedical research at the National Institutes of Health, $1 billion for grants to states for drug abuse prevention and research and $500 million for the FDA to accelerate its approval procedures.

Top Republicans announced the research bill last week, more than a year after the House approved an earlier version by an overwhelmingly bipartisan margin.

Sanders and Warren — two of the highest-profile liberals in Congress — both complained that the bill's money is not guaranteed and must be provided in later legislation by Congress. They also criticized the legislation's savings, which includes cuts in a public health program under President Barack Obama's health care law, reduced payments under Medicare and Medicaid and oil sales from the government's strategic petroleum reserve.

In a speech Monday on the Senate floor, Warren used the populist rhetoric that has made her a hit among progressive voters.

All but demanding that her party follow her lead, she said, "Republicans will control this government, but they cannot hand that control over to big corporations unless Democrats roll over and allow them to do so."

She said the research bill would "legalize fraud" by reducing the scientific evidence the government needs to approve existing drugs for new uses. She said it would "cover up bribery" by exempting medical companies from publicly reporting some payments they make to doctors.

"I cannot vote for this bill. I will fight it because I know the difference between compromise and extortion," said Warren, who some mention as a potential 2020 presidential contender.

Warren also said the bill benefits a Republican donor who backs contentious therapies that are supposed to regenerate cells. She did not name the donor during her speech but said McConnell, R-Ky., has accepted contributions from him.

A Warren spokesman said Warren was referring to an April report by Politico that said separate legislation helping companies get approval for stem-cell treatments was backed by Ed Bosarge, a wealthy Texan. The report said Bosarge has donated to McConnell's political committee and invested in regenerative medicine.

A McConnell spokesman declined to comment. McConnell said this month that the overall bill is a major priority for Congress' lame-duck session and singled out its provisions helping regenerative medicine.

Sen. Charles Grassley, R-Iowa, chairman of the Senate Judiciary Committee, said Monday that he wanted the removal of a provision letting companies not report some payments to doctors. Consumer groups have complained that the payments encourage doctors to prescribe those companies' products.

No. 3 Senate Democratic leader Chuck Schumer of New York is also trying to remove that provision, a Democratic aide said.