Wall Street’s three major debt rating firms are warning Partners HealthCare to stem financial losses or risk a downgrade of its credit rating.

Analysts at Fitch Ratings, S&P Global Ratings, and Moody’s Investors Service revised their credit outlook for Partners from stable to negative, which is more bearish than their view on the nonprofit hospital industry as a whole. Fitch also downgraded Partners’ credit rating by one notch, a troubling sign for the state’s largest health network and largest private employer, which has historically posted steady profits.

The reports, issued over the past several weeks, come after Boston-based Partners announced the worst earnings in its history. The company, whose hospitals include Massachusetts General and Brigham and Women’s, lost $108 million on operations in the fiscal year ended Sept. 30, 2016. Almost all of the losses stemmed from its struggling insurance business, Neighborhood Health Plan, which primarily serves low-income patients on Medicaid. One Partners community hospital, North Shore Medical Center in Salem, also continued to lose money.

Adam Kates, an analyst who worked on the Fitch report, issued last week, said he had expected Neighborhood Health Plan’s finances to turn around by now. Instead, the losses have mounted. “The main question I have is on their ability to turn around Neighborhood Health Plan,’’ he said.

S&P and Moody’s revised their outlooks in late January. They stopped short of downgrading Partners’ credit rating but noted that a downgrade could be the next step. That could make it harder and more expensive for Partners to borrow money for capital spending, such as hospital renovation and expansion projects.

Debt ratings are used by investors to gauge the risk of loaning money to a company. A negative outlook means that the company’s rating is likely to be cut unless it addresses the problems flagged by analysts.

“The message in our report is pretty clear that we would like to see a turnaround in fiscal ‘17. If we don’t, we could consider lowering the rating,’’ said Jennifer J. Soule, an analyst at S&P Global.

Partners is taking steps to shore up finances at Neighborhood Health Plan, including freezing enrollment for people on Medicaid, the government program for people with low incomes. It is also planning to cut up to 200 jobs at North Shore Medical Center to address the losses there.

Partners chief financial officer Peter K. Markell said he was disappointed but not surprised to see the negative outlook from debt analysts. He said the situation will worsen if the state approves new regulations to curb high hospital payments, as proposed by Governor Charlie Baker and a special commission that studied health care prices. Partners has among the most expensive hospitals in Massachusetts and is likely to feel the effects of any rate caps.

Markell warned that the company, which employs about 68,000 people, would have to cut jobs if costs continue to rise but revenue doesn’t. “If we get downgraded, it means our economic model isn’t working, and we’re going to have to change it,’’ he said. “When two-thirds of your costs are labor-driven, you’re going to have to make labor moves.’’

Moody’s analyst Daniel Steingart said his analysis accounted for the fact that Partners is “under the microscope’’ in Massachusetts. In 2015, Partners dropped a plan to acquire three community hospitals amid objections that the deals would give it too much market power and raise health care costs. Partners has since acquired Wentworth-Douglass Hospital in Dover, N.H., and said in January that it wants to acquire Massachusetts Eye and Ear, a specialty hospital in Boston.

“Both the regulatory environment and the public scrutiny that Partners is under in Eastern Massachusetts contributes to a more difficult operating environment,’’ Steingart said.

Partners said it has about $5 billion in outstanding debt, though not all of it is rated. The company has about $6.1 billion in reserves, or 184 days’ cash on hand, according to S&P.

Two temporary factors — a consolidation of office spaces and the implementation of a $1.2 billion new software system — also hit Partners’ earnings, but analysts said those factors were temporary and not major concerns for the company going forward.

The analysts also noted that Partners remains a leader in the local health care market and runs among the country’s most prestigious hospitals.

$5 billion

Partners’ total outstanding debt

McCluskey can be reached at priyanka.mccluskey@globe.com. Follow her on Twitter @priyanka_dayal.