WASHINGTON — Closing the Indian Point nuclear power plants would be costly and difficult, but it could be done if the state and power companies moved quickly and built big new facilities, a group of scientists said Tuesday.

A report by a National Academy of Sciences committee said there is no technological barrier to replacing the twin nuclear power plants on the banks of the Hudson River, but a host of financial and regulatory hurdles are in the way.

Since Sept. 11, 2001, many residents around the plants in Buchanan, N.Y., north of New York City, have worried they are at risk to radiation exposure if terrorists attacked Indian Point.

Federal regulators and the private company that runs Indian Point have repeatedly insisted the site is secure, but that has not stopped the criticism.

Rep. Nita Lowey, D-Westchester, who wants to close Indian Point, had sought a scientific review to determine how New York could do that and still have a reliable power supply. The committee’s findings suggested the growing energy demands in the metropolitan area would make shutting down the reactors difficult.

“The committee has identified no insurmountable technological barriers to the replacement of Indian Point’s capacity, energy and ancillary services, but significant financial, institutional, regulatory and political barriers also would have to be overcome to avoid threatening reliability,” the group said in a 280-page report.

At a news conference in White Plains, N.Y., Lowey said the report’s bottom line was, “We can meet the region’s increasing energy demands without Indian Point.” Speaking next to a poster showing energy-efficient air conditioners and fluorescent light bulbs, she said the goal could be accomplished with conservation, transmission improvements and “modest new generation.”

The problem, the report argues, is that Indian Point now cranks out nearly one-quarter of the power consumed by the region encompassing New York City and its suburbs, and demand for power is growing fast.

“Even with the Indian Point units operational, New York state will require system reinforcements, above those already under construction, as soon as 2008 in order to meet its projected demand for electricity and maintain system reliability,” the committee found.

The report, by design, took no position on whether Indian Point should be closed. Several members of the committee attended Lowey’s news conference, but the chairman, Lawrence Papay of the National Academy of Engineering, said they were there to answer questions, not to support Lowey’s position.

The committee warned that generating capacity in the New York City area may be outstripped by peak demand in as little as three years.

Indian Point is a 2,000 megawatt facility, and the state’s power needs are expected to grow between 1,200 and 1,600 megawatts by 2010.

The experts also suggested public resistance, bureaucratic delay and market forces may slow the expansion of needed power plants until the demand reaches a crisis point.

“New generating capacity may not be available until reserves are dangerously low. Forestalling a crisis may require extraordinary efforts on the part of policy makers and regulators,” the report said.

A spokesman for the plants’ owner, Entergy Nuclear Northeast, praised the report, saying, “It’s actually a good illustration of the value of the plant.”

“They not only point out the hurdles that would have to be overcome to close the plant, they point out the toxic gases, the contribution to global warming, seeing electricity costs rise,” said spokesman Jim Steets.

The New York Affordable Reliable Electricity Alliance, an industry group, said the report shows “that in the real world of politics, our economy and our environment it would be extremely difficult to replace this critical element of our energy infrastructure.”

The scientists envision two scenarios, one which would close Indian Point at the end of the decade, and one that would shut the two plants in 2013 and 2015.

The earlier closure “would be much more difficult to accomplish” at a time when “New York will have very little if any excess capacity,” they wrote.

The plants could be retired in 2013 and 2015 if New York ramped up its energy production by bringing 500 more megawatts to the system every year for a decade.

But replacing Indian Point wouldn’t be cheap. Depending on who would pay for closing Indian Point, those extra costs could end up in residents’ power bills.

A separate study commissioned last year by Westchester County concluded that Entergy should be offered up to $1.4 billion to voluntarily shut down Indian Point. Steets said Tuesday, “There certainly hasn’t been any movement in that direction.”

Lowey said that amount would be “subject to negotiation.”