Senate Majority Leader Mitch McConnell on Monday night abruptly called for a vote to repeal Obamacare without an immediate replacement after the latest Republican effort to overhaul the U.S. health-care system fizzled out.

"Regretfully, it's now apparent that the effort to repeal and immediately replace the failure of Obamacare will not be successful," McConnell said in a statement. "So, in the coming days, the Senate will vote to take up the House bill with the first amendment in order being what a majority of the Senate has already supported in 2015 and that was vetoed by then-President Obama: a repeal of Obamacare with a two-year delay to provide for a stable transition period to a patient-centered health care system that gives Americans access to quality, affordable care."

President Donald Trump, who had pressed for a repeal and replacement plan, urged Republican lawmakers to repeal Obamacare first, and then come up with a solution for replacing it. It is unclear if the GOP has the votes to repeal the law without an immediate replacement, as it risks destabilizing insurance markets.

Donald Tweet: Republicans should just REPEAL failing ObamaCare now & work on a new Healthcare Plan that will start from a clean slate. Dems will join in!

Earlier Monday, two more Republican senators said they would oppose the current Republican health-care bill — enough to doom its passage barring changes.

In messages posted to Twitter, Sens. Jerry Moran, R-Kan., and Mike Lee, R-Utah, became the third and fourth GOP senators to say they would not support their party's Obamacare replacement plan as written. They said they would not even back a motion to allow a procedural vote that would have started debate on the bill. The GOP, which holds 52 seats in the Senate, had already seen two defections and could not afford a third.