Sen. Susan Collins, R-Maine, revealed Monday that she will vote against the Graham-Cassidy bill that would repeal and replace major parts of Obamacare, likely dooming Republican efforts to get rid of that health-care law.

Collins is the third Republican senator after John McCain of Arizona and Rand Paul of Kentucky to publicly say they will vote "no" on Graham-Cassidy.

Earlier Monday, President Donald Trump said the failure by his fellow Republicans in Congress to pass Obamacare repeal as long promised was "disgusting," and that he expected Collins to kill the latest effort by opposing the bill.

GOP leaders need 50 of their 52-member majority in the Senate to vote for the bill to win passage before a deadline Saturday.

Collins' move came minutes after the Congressional Budget Office in a preliminary analysis said that if the bill becomes law the number of people with health insurance that covers "high-cost medical events would be reduced by millions."

And it came hours after the release of a new version of Graham-Cassidy that was tweaked to direct more federal funds to Collins' home state of Maine, as well as to the states of several other Republican holdouts to the bill.

In announcing her opposition, Collins cited the CBO report, among other factors.

"The CBO's analysis on the earlier version of the bill, incomplete though it is due to time constraints, confirms that this bill will have a substantially negative impact on the number of people covered by insurance," Collins said.

Collins also cited the rushed effort to pass Graham-Cassidy, the risks that the bill poses to Medicaid, and the danger of the legislation undercutting Obamacare protections for people with pre-existing health conditions.

"Sweeping reforms to our health care system and to Medicaid can't be done well in a compressed time frame, especially when the actual bill is a moving target," Collins said.

"Today, we find out that there is now a fourth version of the Graham-Cassidy proposal, which is as deeply flawed as the previous iterations. The fact that a new version of this bill was released the very week we are supposed to vote compounds the problem."

Earlier Monday, S&P Global Ratings issued two reports that estimated Graham-Cassidy would lead to job losses of nearly 600,000 people, and cost $240 billion in lost economic activity over the next decade, as well as threatening the fiscal outlooks of state and local governments.

The CBO report issued Monday analyzed, in preliminary fashion, the effect of an earlier version of Graham-Cassidy. Another version of the bill was rolled out Monday.

CBO, in its report on the bill, said the number of newly uninsured "could vary widely depending on how states implemented" Graham-Cassidy.

"The decrease in the number of insured people would be particularly large starting in 2020," the non-partisan CBO said in its new report.

That year is when Graham-Cassidy would begin making major changes in how the federal government funds Medicaid and provides assistance to people buying health coverage in the individual plan market.

CBO pointedly noted that the report does not offer specific estimates on exactly how many people are expected to become uninsured.

Nor does the preliminary report estimate how Graham-Cassidy would affect individual market insurance premiums or its total expected impact on the federal budget deficit.

CBO said it would need "at least several weeks to provide" such specific projections.

Past reports by the CBO on recent Republican bills to repeal Obamacare estimated that up to 21 million people or more would become uninsured by 2026 if those bills became law, as compared with the Affordable Care Act remaining intact.

The report was rushed at the behest of Senate Majority Leader Mitch McConnell, R-Ky., in an effort to pass Graham-Cassidy before a deadline this Saturday.

The deadline is the result of the Republicans using a process known as budget reconciliation to allow passage of a repeal effort with just 50 votes, as opposed to the 60 votes traditionally needed with other legislation to avoid being blocked by a filibuster. The Senate parliamentarian ruled Sept. 1 that the reconciliation authorization expires this Saturday.

Despite the lower vote hurdle, McConnell for months has been unable to cobble together the 50 Republican senators he needs to pass a repeal bill, assuming a tie-breaking vote from Vice President Mike Pence, himself a Republican.

Last week, McCain said he would oppose the bill. On Monday, Paul restated his opposition to a new version of the bill.

While Paul had voted for an Obamacare replacement bill in July, McCain had dramatically voted against it, sending it down to defeat.

In that vote, McCain was joined by Collins and Sen. Lisa Murkowski of Alaska, along with every Democrat and independent in the Senate.

Murkowski has yet to declare her position on Graham-Cassidy.

Read Collins' full statement opposing Graham-Cassidy, below: