The nation's first offshore wind farm faces more delay after a top Massachusetts historic preservation officer said that two Indian tribes' claim to Nantucket Sound needed more study.

The decision by Brona Simon, executive director of the Massachusetts Historical Society, means final approval for the Cape Wind project, proposed in 2001, will be delayed by weeks and perhaps months.

Cape Wind seemed near final approval after it passed a major environmental review in January, but that's been delayed by the Wampanoag tribes in Mashpee and Martha's Vineyard.

The tribes argue the entire sound is eligible for a listing on the National Register of Historic Places as their "traditional cultural property."

The Wampanoags say they need that protection because Cape Wind's 130 turbines will be visible several miles away on the horizon, destroying their ancient rituals, which require an unblocked view of the sunrise.

Mark Rodgers, a spokesman for Cape Wind, said he was disappointed with the finding but confident that the project will move forward.

"We think it's flawed," Rodgers said. "The only negative is that it's going to result in some minor delay."

A call to a Wampanoag spokesman was not immediately returned Thursday.

Simon said the commission found "considerable archaeological, historical, and ethnographic information that substantiates that Nantucket Sound is historically significant."

Cape Wind advocates, including energy and economic development heads in Gov. Deval Patrick's administration, have said the claim has no merit.

They argued that a vast, unenclosed area such as Nantucket Sound isn't eligible for the national register and that the new regulations in Nantucket Sound would damage a host of commercial activities. Continued...