Mr. Cuomo, a Democrat who has generally avoided national politics even as he is often mentioned as a potential candidate for president, offered an enthusiastic endorsement of the benefits of the health care measure, which is currently being litigated before the Supreme Court and contested in this year’s presidential campaign.
As he issued an executive order to establish a health insurance exchange, an online marketplace where individuals and small businesses can choose among competing health insurance plans, Mr. Cuomo said it would drive down the cost of insurance while helping the 2.7 million uninsured New Yorkers get affordable coverage.
“The bottom line,” Mr. Cuomo said in a statement, “is that creating this health exchange will lower the cost of health insurance for small businesses, local governments and individual New Yorkers across the state.”
For nearly a year, Mr. Cuomo asked the Legislature to set up the exchange. But the Republican majority in the State Senate refused to consider the measure, arguing that approving the exchange would amount to condoning the law, the Affordable Care Act, which they deride as Obamacare.
The Senate Republicans also cited the uncertainty surrounding the health care law, given the Supreme Court challenge, and last month, they blocked Mr. Cuomo from including the exchange in the state budget for the fiscal year that began April 1.
The health care law requires each state to put an insurance exchange in place by 2014, and gives the federal government the power to do so in states that do not act on their own.
Mr. Cuomo, unable to win support for the exchange in the State Senate, vowed to move ahead unilaterally, and on Thursday, he signed the order to set up the exchange within the State Health Department, rather than as a separate state entity, as his original legislation had sought to do.
Mr. Cuomo’s order drew praise on Thursday from Democratic lawmakers, health advocacy groups and leaders in the state’s health care industry. Kenneth E. Raske, the president of the Greater New York Hospital Association, called the move “a way of alleviating the current crisis facing those that don’t have access to care because of lack of insurance.”
But Mr. Cuomo’s move irked some conservatives, who are determined to fight the health care law and view state capitals as important battlegrounds in which the law’s implementation can be contested.
State Senator Gregory R. Ball, Republican of Putnam County, who has been one of the most vocal critics of the health exchange proposal, said Mr.
Cuomo was acting prematurely, given the Supreme Court case. Mr. Ball also criticized the governor for “sidestepping the Legislature” to set up the exchange.
“Enlisting our state in a program that may cease to exist on both constitutional and administrative grounds is, in my opinion, overly aggressive and fundamentally imprudent,” Mr. Ball said.
Michael F. Cannon, the director of health policy studies at the Cato Institute, a libertarian research center in Washington, said that refusing to pass legislation to set up a health exchange was “the most powerful blow that a state can strike against Obamacare,” and questioned Mr. Cuomo’s use of an executive order.
“King Andrew shouldn’t be out creating new bureaucracies on his own,” Mr. Cannon said. “If the people’s elected representatives say they don’t want to create a new government bureaucracy, then the government doesn’t have the power to create a new government bureaucracy.”
Since the passage of the Affordable Care Act, 11 states have set up insurance exchanges, according to the National Conference of State Legislatures.
Ten did so with legislation; only one — Rhode Island — used an executive order, and a lawsuit challenging the authority of that order is pending.
Mr. Cuomo’s office defended the use of an executive order, noting that the state would rely on federal financing to set up the exchange, rather than any new state spending, and that it would not set up a new governmental body. New York has already received $88 million in federal grants to plan for its health exchange; setting up the exchange will allow the state to seek additional federal financing.
“The activities that are necessary to implement the exchange are within the existing legal authority of the Department of Health, in which it will be based, and the other agencies with which it will work, including the Department of Financial Services,” Mr. Cuomo’s counsel, Mylan L. Denerstein, said in a statement.
Peter J. Kiernan, who served as chief counsel for former Gov. David A. Paterson, a Democrat, said that although “legislation is always optimal,” he believed the executive order was legal.
“In essence, he’s telling the Department of Health, which works for him, to get ready to do this, and to use federal money that has already come through,” Mr. Kiernan said. “There may be people that would complain about it, but I don’t think that anyone would be successful challenging the governor’s authority here.”
A spokesman for the Senate Republicans declined to comment on the executive order. But after Mr. Cuomo said last month that he would set up the exchange using his own power, the Senate majority leader, Dean G. Skelos, a Long Island Republican, said the Senate Republicans would not be interested in challenging such a move.
“The governor has the right to issue executive orders,” Mr. Skelos said. Still, he added, “If somebody wants to sue him, fine.”