Mitch McConnell. Alex Wong/Getty Images Republicans on Tuesday decided against bringing the Graham-Cassidy healthcare bill to the floor for a vote, a GOP aide told Business Insider, effectively killing the party's latest push to overhaul the US healthcare system.

Sens. Lindsey Graham and Bill Cassidy, two of the authors of the bill, said during a press conference with GOP Senate leaders that there were not enough votes to pass the measure.

"Well, to be clear, due to events under our control and not under our control, we do not have the votes," Cassidy said.

Graham said it was "not if but when" Republicans would pass his healthcare bill, but added that there was still work to be done before then.

"We know what we're against," Graham said. "We've had a hard time articulating what we're for."

Senate Majority Leader Mitch McConnell said the GOP conference would move on from the push to repeal and replace the Affordable Care Act, the law better known as Obamacare, to the attempt to reform the tax code.

It became apparent on Monday that Republicans did not have the 50 votes needed to get the bill through the Senate when Sen. Susan Collins announced her opposition to the bill, making her the third Republican senator to defect. Republicans hold 52 seats in the Senate.

Republicans' ability to use fiscal 2017 budget reconciliation, which allows for certain bills to pass with a simple majority, will expire on Saturday. After that, Democrats will be able to filibuster any healthcare bill put forward.

That means the GOP must either work with Democrats to get eight more votes on a healthcare bill or wait to mount another effort under reconciliation rules in either the fiscal 2018 or the fiscal 2019 budget.

"Look, we haven't given up on changing the American healthcare system. We're not going to do that this week," McConnell said. "But it still lies ahead of us."