A few months after Gov. Andrew M. Cuomowas poised to approve hydraulic fracturing in several struggling New York counties, his administration is reversing course and starting the regulatory process over, garnering praise from environmental groups and stirring anger among industry executives and upstate landowners.

Ten days ago, after nearly four years of review by state regulators, the governor bowed to entreaties from environmentalists to conduct another study, this one an examination of potential impacts on public health. Neither the governor nor other state officials have given any indication of how long the study might take.

Then on Friday, state environmental officials said they would restart the regulatory rule-making process, requiring them to repeat a number of formal steps, including holding a public hearing, and almost certainly pushing a decision into next year.

The move also means that after already receiving nearly 80,000 public comments, the state Department of Environmental Conservation will be soliciting more input from New Yorkers about hydrofracking, or fracking, as the drilling process for natural gas is known.

The developments have created a sense in Albany that Mr. Cuomo is consigning fracking to oblivion. The governor has been influenced by the unshakable opposition from a corps of environmentalists and celebrity activists who are concerned about the safety of the water supply. The opponents include a number of people close to the governor, including Robert F. Kennedy Jr., a longtime environmental activist in New York whose sister is the governor’s ex-wife.

The fracking issue is the biggest environmental question, and the most polarizing, facing Albany, and New York’s decision is being closely watched nationally, as President Obama and Mitt Romney have both expressed support for increased use of natural gas as a means to reduce the nation’s dependence on foreign oil. The natural gas industry has been eager to drill in the Marcellus Shale, a deep underground repository that runs through West Virginia, Ohio, Pennsylvania and New York. Extraction there was too complex and costly until the advent of hydrofracking.

The debate is politically complex for Mr. Cuomo, who has established a record as a social progressive and a fiscal centrist. Mr. Cuomo has been interested in fracking because of the promise that it could bring jobs to an economically struggling region of the state. The industry has also been a prolific campaign donor, and rejecting fracking would risk Mr. Cuomo’s close relationship with The New York Post, which has strongly advocated for drilling.

But opposition to fracking has become such a touchstone for liberals that approving it, even in a limited fashion, would undoubtedly alienate some of his most dependable supporters. Anti-fracking protesters have shadowed Mr. Cuomo for months, at his home, his office, and his speaking engagements, and a wide array of celebrities, including Lady Gaga and Yoko Ono, have mobilized to express opposition to the technology.

“Andrew has a very good political antenna, and we’ve never seen anything like this in terms of grass-roots power,” Mr. Kennedy, whose father was a United States attorney general, said in a telephone interview. “In 30 years, I have not seen anything come close to this, in terms of the mobilization of the grass roots. You’ve got 20,000 people in the state who consider themselves to be anti-frack activists. So I think that’s got to impact the political process all around.”

The governor appointed Mr. Kennedy, who lives in Westchester County, to an advisory panel on fracking last year, and Mr. Kennedy has been in frequent contact with the governor and his staff about the issue.

Mr. Kennedy said that he and the governor had discussed the research on fracking, including examinations of how frequently the concrete well casings used in fracking fail, exposing potential toxins. He said they had also discussed a March study from the Colorado School of Public Health that found that people living near fracking sites were more likely to be exposed to harmful air pollutants like benzene and toluene.

“I’m surprised how long he’s withstood the tide,” Mr. Kennedy said of the governor. “I’m proud that he’s done that. There’s no other governor who’s just said ‘let’s hold off.’ And he’s under, I can tell you, tremendous pressure by the industry and by others.”

Mr. Cuomo told reporters last week that the commission of yet another study on fracking did not signal an end to the process.

“We’ve said all along that the decision will be made based on the science, right?” he said. “It was not predetermined, it was not a political position, let’s get the facts, let’s make a decision on the facts. I understand the emotion, I deal with the emotion every day on both sides of the issue, right? So we get the emotion, we get the rhetoric, we get the hyperbole. Let’s get some facts and data and some science, and we’ll make the decision on the science, which is what should be done here.”

The governor has also said that he sees the additional health study as a way to mitigate future lawsuits.

Katherine Nadeau, a program director at Environmental Advocates of New York, said talk of an end to fracking was premature.

“From what I can tell, it doesn’t seem to me that the administration is necessarily backing off, but they are listening to the enormous public concern and outcry and making sure to take this incredibly slowly,” she said.

But industry and landowner groups are growing increasingly concerned about the shifting tone toward fracking expressed at the Capitol.

Brad Gill, executive director of the Independent Oil and Gas Association of New York, an industry group, said that while some of his members “have made the decision to move on, those that remain are taking Governor Cuomo at his word. But they are also struggling.”

“After four years of waiting, any additional unforeseen circumstance, irrespective of its merit or cause, places an extraordinary burden on those fighting to be part of a new New York,” he added, referring to one of Mr. Cuomo’s campaign slogans.

Scott Kurkoski, the lead lawyer for the Joint Landowners Coalition of New York, a pro-fracking group, was more pointed.

“The part that concerns us is our governor has said he wants to keep it out of politics and focus on the science, but it looks like politics is really taking over now,” he said, adding that some smaller landowners who were hoping to lease out their land for fracking were facing foreclosure.

“I don’t think the governor cares about the plight of the upstate New York landowners,” he said.

In horizontal hydraulic fracturing, large volumes of water and chemicals are injected deep underground at high pressures to break up rock formations and release pockets of natural gas. In the late spring, the administration had drawn up a plan to approve fracking in portions of several New York counties located west of the Catskills, along the border with Pennsylvania, and to permit it only in communities that express support.

But that plan only hardened opposition.

“The governor’s office is moving cautiously by floating solutions and listening to the critiques,” Mr. Kennedy said. “You really feel like there’s some democracy happening here.”

It was not entirely clear what further health impacts would be studied that were not already encompassed by the review process that began in the summer of 2008. In a statement in response to questions, the Department of Environmental Conservation said “health impacts were not overlooked” in the agency’s prior reviews, and “were fully assessed” in a draft environmental impact study that was released last year.

Joseph Martens, the agency’s commissioner, said last week: “Obviously if there was a public health concern that could not be addressed we would not proceed.”

Senator Thomas W. Libous, a Binghamton Republican and leading proponent of fracking, said he hoped the new study was “the last major hurdle,” adding, “I want to believe that.”