The latest Republican effort to repeal and replace "Obamacare" was fatally wounded in the US Senate on Monday night when two more Republican senators announced their opposition to the legislation strongly backed by President Donald Trump.

The announcements from Senators Mike Lee of Utah and Jerry Moran of Kansas left the Republican Party's long-promised efforts to get rid of former President Barack Obama's healthcare legislation reeling. Next steps, if any, were not immediately clear.

Lee and Moran both said they could not support Majority Leader Mitch McConnell's legislation in its current form. They joined Republican Senators Susan Collins of Maine and Rand Paul of Kentucky, both of whom announced their opposition right after McConnell released the bill last Thursday.

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In a senate divided 52-48 between Republicans and Democrats, McConnell could lose only two senators and still prevail on a procedural vote to open debate on the bill.

There are at least a half-dozen or so others who are undecided, so it's quite likely that more "no" votes will be announced in the hours and days ahead.

McConnell is now at least two votes short in the closely divided senate and may have to go back to the drawing board or even begin to negotiate with Democrats, a prospect he's threatened but resisted so far. Or he could abandon the healthcare effort, which has proven more difficult than many Republicans envisioned after campaigning on the issue for years, and move on to tax legislation, a bigger Trump priority to begin with.

McConnell's bill "fails to repeal the Affordable Care Act or address healthcare's rising costs. For the same reasons I could not support the previous version of this bill, I cannot support this one," said Moran.

Lee said, "In addition to not repealing all of the Obamacare taxes, it doesn't go far enough in lowering premiums for middle-class families; nor does it create enough free space from the most costly Obamacare regulations."

It was the second straight failure for McConnell, who had to cancel a vote on an earlier version of the bill last month when defeat became inevitable.

Trump had kept his distance from the senate process, but Monday night's development was a major blow for him, too, as the president failed to rally support for what has been the Republican Party's trademark issue for seven years - ever since Obama and the Democrats passed the Affordable Care Act.

Republicans won the White House and full control of congress in large part on the basis of their promises to repeal and replace "Obamacare," but have struggled to overcome their deep internal divisions and deliver.

Al Jazeera's Heidi Zhou-Castro, reporting from Washington, DC, said it showed the scale of the lack of consensus and unity in the Republican Party.

"The two wings of the party - the moderates and the conservatives - are just so far apart on this one, with competing priorities, that they simply could not find common ground."

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The senate bill, like an earlier version that barely passed the House, eliminated mandates and taxes under Obamacare and unravelled an expansion of the Medicaid healthcare programme for the poor and disabled.

But for conservatives like Lee and Paul, it didn't go far enough in delivering on Republican Party promises to undo Obama's law, while moderates like Collins viewed the bill as too extreme in yanking insurance coverage from millions.

McConnell's latest version aimed to satisfy both camps, by incorporating language by Senator Ted Cruz of Texas allowing insurers to sell skimpy plans alongside more robust ones, and by adding billions to treat opioid addiction and to defray consumer costs.

But his efforts did not achieve the intended result.

'Republicans should start from scratch'

"This second failure of Trumpcare is proof positive that the core of this bill is unworkable," said Democrat Senate Minority Leader Chuck Schumer of New York.

"Rather than repeating the same failed, partisan process yet again, Republicans should start from scratch and work with Democrats on a bill that lowers premiums, provides long term stability to the markets and improves our healthcare system."

Al Jazeera's Heidi Zhou-Castro said Republicans had attempted now for seven years to undo Obama's signature healthcare legislation.

"In that time they have managed to gain control of both chambers of congress, as well as elect Donald Trump - their president - to the White House. And despite those gains, they were unable to come up with a better alternative to replace Obamacare," she said.

The next step could be to reach out to Democrats who have acknowledged flaws in Obamacare, to reach some kind of bi-partisan consensus, said our correspondent.

"Bi-partisanship is unfamiliar territory here, but this may be the door that finally opens it," said Zhou-Castro.