House Republicans snagged a few more supporters for their Obamacare repeal-and-replace bill after promising to plump it up with $8 billion to help those with pre-existing conditions pay for their health care — part of a high-stakes push to win over moderate GOP lawmakers who have balked at the legislation. The White House has been ramping up pressure for a vote on the bill this week.

"I support the bill with this amendment," said Rep. Fred Upton, R-Mich., after meeting with President Trump at the White House on Wednesday morning. Upton is an influential player on health care policy, and he had previously opposed the bill amid concerns it would undermine protections for people with pre-existing conditions.

Another holdout, Rep. Billy Long, R-Mo., also switched from a "no" to a "yes" after meeting with Trump. He said his GOP colleagues "sold" him on the amendment.

The biggest sticking point so far: the provision in Obamacare that bars insurance companies from discriminating against those with pre-existing conditions. The current GOP bill would dramatically undermine that, by allowing insurance companies charge people with pre-existing conditions —anything from cancer to pregnancy — higher premiums than other consumers.

That change prompted Upton's push to add the extra $8 billion to help sicker patients pay their premiums and other health care bills. Upton is the former chairman of the House Energy and Commerce Committee, which has played a central role in drafting the GOP bill, called the American Health Care Act.

With Democrats unified against the measure, GOP leaders can only lose about 22 Republicans and still pass the bill. By multiple news outlets’ counts, roughly 20 lawmakers said they’d vote “no” as of Tuesday afternoon and about two dozen others remained undecided.

With the new money, Republicans expressed confidence that they could win passage of the bill, although they would not say when they might bring it up for a House vote. It was also unclear whether the $8 billion amendment would cause hard-line conservatives to back away from their support. The bill has been a tug-of-war between the moderate and conservative factions inside the House Republican Conference during weeks of intense negotiations and embarrassing setbacks.

Vice President Pence is on Capitol Hill talking to members of Congress, White House press secretary Sean Spicer said Wednesday afternoon. Spicer also said it's up the House leadership to schedule a vote, but "we continue to move closer and closer to that time."

In a series of radio interviews Wednesday, House Speaker Paul Ryan, R-Wis., said Republicans were getting “extremely close” to having the votes they need in the House. But asked by WCLO radio in his hometown of Janesville whether there would be a vote this week, Ryan said, “We haven’t made that decision yet.”

He touted the latest changes to the bill, asserting that with added funding for high-risk pools, “we’re making sure that we have three or four layers of protections for people with pre-existing conditions.” Ryan also said that by promoting high-risk pools and directly subsidizing people with catastrophic illnesses, “you dramatically lower the price of premiums for everyone else buying health insurance.”

But critics said the Upton provision was still woefully inadequate to protect those with pre-existing conditions, and they noted that the Congressional Budget Office estimated an earlier version of the legislation would cause 24 million people to either forgo or lose their health insurance.

“Despite today’s wheeling and dealing, the GOP repeal bill still drops the coverage guarantee for people with pre-existing conditions, strips coverage from millions, and drives up costs for millions more," said Frederick Isasi, executive director of Families USA, a liberal-leaning health advocacy group. "A measly $8 billion handout isn’t going to change that."

And some Republicans reaffirmed their opposition to the bill and blasted the latest changes as Washington at its worst.

"The AHCA is like a kidney stone — the House doesn't care what happens to it, as long as they can pass it," Rep. Thomas Massie, R-Ky., said in a tweet on Wednesday.

The GOP bill would repeal major elements of the 2010 Affordable Care Act and allow states to opt out of other provisions, including several popular consumer protections. For example, states could seek a waiver from existing requirements that insurers must cover maternity care, substance abuse and other key health services.

States can also seek an exemption of the pre-existing condition protections, allowing insurers to charge such patients more if the state has created a high-risk pool. Such risk-sharing programs are intended to help lower patient costs, but they have had mixed results in the past.

Contributing: David Jackson, Eliza Collins and Craig Gilbert