House Speaker Paul Ryan, the Wisconsin Republican. Win McNamee/Getty Images Fresh optimism displayed by White House and some House GOP officials at the beginning of the week has turned into a familiar mad dash to secure votes needed to pass the Republican healthcare-overhaul plan in the House.

The growing number of GOP lawmakers coming out publicly against the new version of the American Health Care Act — the bill to repeal and replace Obamacare — has already put the plan on a razor's edge of support. Leadership is attempting to shore up the centrist wing of the party by introducing new funding to protect sick Americans.

House Speaker Paul Ryan told conservative radio host Hugh Hewitt on Wednesday that Republicans were "extremely close" to securing enough votes to pass the legislation, but he did not say whether the bill would come to a vote this week.

The main sticking point is an amendment added by Rep. Tom MacArthur, a centrist member from New Jersey who has long supported the AHCA. The amendment to the legislation that has also become known as "Trumpcare" was designed to win over conservatives.

It would allow states to apply for waivers to repeal parts of Obamacare's protections if they can prove it would lower costs. Conservatives members support the addition because they say it gives more flexibility to the states and gets closer to an full repeal of the Affordable Care Act.

On the other hand, some House GOP members, especially moderates, have expressed concerns about the latest version of the bill, because many health-policy analysts say the addition could undermine protections for people with preexisting conditions.

To counter their concerns, Rep. Fred Upton, who came out against the current version of the AHCA with the MacArthur amendment, is expected to introduce his own addition on Wednesday.

It's not yet clear what the final version of the legislation would look like. Axios reported Wednesday that Upton's addition would help soften the blow of the penalty incurred by people who allow their insurance to lapse, in an effort to protect people with preexisting conditions.

The Independent Journal Review, however, reported Tuesday night that the amendment would instead call for additional $8 billion in funding for the AHCA's state stability funds. The legislation already proposes for $150 billion to be allocated over 10 years for the funds, which would go toward supporting things like high-risk pools and offsetting high costs for poorer Americans.

The changes appear to have won over Upton, who said the bill is "likely now to pass in the House," and fellow hold out Rep. Billy Long.

But concerns have mounted that any addition to the bill could cause conservatives like those in the House Freedom Caucus to drop their tenuous support of the bill.

The last-ditch efforts come after White House and House GOP leaders pledged to get the healthcare bill through the House this week, setting another artificial deadline that has ramped up pressure to deliver the votes.

President Donald Trump said during a speech on Tuesday that "now is the time" to pass the healthcare bill and leaders from Vice President Mike Pence to House Majority Leader Kevin McCarthy told the press that the bill would pass this week during appearances over the weekend.

There is also a growing sense that Republicans just want to get the bill through, no matter what the circumstances.

Rep. Tom Cole told Politico that the leadership would "throw every sink in every kitchen they can find" to get the bill passed.

Republican senators have been similarly exasperated at the false starts and unsuccessful attempts to get the AHCA through the lower chamber. One Republican senator told Politico that House GOP leadership needs to focus on just getting the bill to the Senate.

"Getting that bill out of there no matter what it says or what’s in it should probably be the No. 1 priority of the House leadership," the senator said.