New Jersey Gov. Chris Christie (R) announced Thursday that he would pull out of a regional climate pact by the end of the year, delivering a political setback to the fledging effort to curb greenhouse gas emissions linked to global warming.

In a news conference, Christie said the Regional Greenhouse Gas Initiative (RGGI), a 2005 accord in which 10 states agreed to cut greenhouse gas emissions from power plants 10 percent by 2018, would not be able to meet its goals.

The program requires plants in the region that burn fossil fuels to buy pollution allowances for the carbon they emit, which they can trade among themselves. It took effect in 2008, making it the first cap on greenhouse gas emissions implemented in the United States.

But Republican gains in last fall’s elections on both the state and national levels have prompted a reexamination of such programs in the Northeast, as well as in the Midwest and West. Questions are being raised about the extent to which these regional initiatives can cut greenhouse gas emissions without mandatory federal limits. In addition to New Jersey, states in the RGGI are Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New York, Rhode Island and Vermont.

Christie said he did not question that human activity plays at least a partial role in warming the planet: “I’ve always said that climate change is real and it’s impacting our state.” But he said that he and his staff believe the regional program would do little to offset the problem.

“This program is not effective in reducing greenhouse gases and is unlikely to be in the future,” he said. “The whole system is not working as it was intended to work. It is a failure.”

Christie emphasized that his decision to withdraw from RGGI did not mean the state was dropping its efforts toward clean energy. As a sign of his commitment to energy alternatives, he said that he opposed building any new coal-fired power plants in New Jersey.

The governor’s change in policy drew swift criticism from environmentalists and New Jersey Democrats, who control the legislature but have no authority to stop Christie from ending the state’s participation in the program.

“In the last six months, several Northeastern states have taken a hard look at RGGI, and in every case, the state legislatures have reaffirmed RGGI’s contributions to job creation, energy efficiency, energy security and economic competitiveness,” said Peter Rothstein, president of the New England Clean Energy Council. “In each of these states, the clean tech and broader business communities came out in favor of RGGI because departure would send a danger signal to companies considering new clean tech investments in these states.”

Democratic Assemblyman John McKeon, who chairs State Assembly’s environment committee, said, “Sadly, this day will go down in history as the one in which New Jersey ceded its standing as a leader in environmental protection efforts.”

Christie is not the first Republican governor to opt out of a regional climate accord. Arizona Gov. Jan Brewer signed an executive order more than a year ago withdrawing from the Western Climate Initiative. But Christie’s decision is more significant because RGGI is already up and running.

Other politicians in New England have taken aim at the program recently, but with mixed success. The New Hampshire House of Representatives passed a bill by a wide margin that would withdraw the state from the program, but earlier this month the state Senate passed a measure that would allow New Hampshire to exit the accord if a major state such as Massachusetts or Connecticut withdrew. The two bills have yet to be reconciled.

Just after the New Hampshire vote, members of Delaware’s House Energy Committee voted to table a bill that would pull the state out of RGGI, preventing the measure from being considered in the full House.