ALBANY (AP) - A critical bloc in New York’s Senate is calling for up to a two-year delay in hydraulic fracturing for natural gas until an independent health review known as the Geisinger study is completed.

The Independent Democratic Conference, which shares control of the Senate with Republicans, said the Geisinger study and two other reviews on drinking water must be completed before Gov. Andrew Cuomo settles the five-year-old debate.

“We have to put science first. We have to put the health of New Yorkers first,” said Sen. David Carlucci, an IDC member representing Rockland and Westchester counties.

“We cannot afford to make a mistake,” said Sen. Diane Savino of Staten Island, another IDC member. “We are going to do this the right way, or we are not going to do it at all.”

Powerful Assembly Speaker Sheldon Silver says he plans an announcement Wednesday to halt the issuing of specific natural gas drilling permits until May 15, 2015. His chamber already calls for a two-year moratorium.

Andy Deubler, an executive vice president at Geisinger Health System in Pennsylvania, which would conduct the study, said having results within a year would be “a stretch.” He said the study will be a 20-year project, broken into five-year segments, and not all the funding required is yet in hand.

Cuomo said late Monday that he hasn’t given a deadline for the state health and environmental conservation commissioners he appointed to advise him on a decision on whether to drill for gas using hydraulic fracturing, or fracking, which injects a mix of water and chemicals thousands of feet underground to crack open shale and release natural gas.

“We reject any call for further delay because the Department of Environmental Conservation and the Health Department are perfectly capable of protecting New Yorkers,” said Jim Smith, spokesman for the Independent Oil and Gas Association of New York. “Further delay is a transparent attempt to stall, and there’s no reason to stall based on science.”

“We believe the political forces are stronger than the scientific forces, and that is what is at play,” Smith said.

Many federal and state regulators say fracking is safe when done properly and thousands of sites have few complaints of pollution. But environmental groups and some doctors say regulations still aren’t stringent enough and the practice can pollute ground water. The Marcellus Shale lies under parts of New York, Pennsylvania, Ohio and West Virginia.

The Associated Press reported over the weekend that environmental lawyer Robert F. Kennedy Jr. discussed the Geisinger report in recent weeks with Cuomo, his former brother-in-law. Kennedy, brother of Cuomo’s ex-wife, Kerry, called the Geisinger report “pivotal” when he and several others spoke to Cuomo.

The conversation came at a time when the momentum to approve limited drilling brought Cuomo closer than ever to approving a limited number of wells that would be closely monitored, though Cuomo hadn’t made a decision, according to two people familiar with Cuomo’s thinking at the time.

The state has had a moratorium on the process since 2008 while other states in the gas-rich Marcellus Shale formation have seen local economies boom as drilling rigs have sprouted up.

Kennedy “is a leader and an environmental activist and his opinion carries weight,” said Kate Hudson, the watershed program director at the environmental group Riverkeeper, which works with Kennedy on legal action to protect the environment.

Cuomo on Monday confirmed he discussed the issue with Kennedy but said he hadn’t made a decision to approve or reject the process, which could provide much-needed jobs in economically depressed southern New York towns.

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Associated Press writer Kevin Begos contributed to this report from Pittsburgh.