BOSTON (Reuters) - The first U.S. offshore wind farm, a giant project 5 miles/8 km off the Massachusetts coast, was approved on Wednesday after years of opposition involving everyone from local Indian tribes to the Kennedy family.

A power-generating windmill turbine operates in a wind farm on Backbone Mountain near Thomas, West Virginia August 28, 2006. REUTERS/Jonathan Ernst

U.S. Interior Secretary Ken Salazar gave the green light for the historic 130-turbine, 420-megawatt Cape Wind project in Horseshoe Shoal, Nantucket Sound, in what supporters considered a huge step forward for renewable energy in the United States.

“This project fits with the tradition of sustainable development in the area,” Salazar said in Boston.

Although small in terms of its production -- the facility would produce enough electricity to power 400,000 houses -- its approval was encouraging to other offshore wind projects already proposed for the East Coast and Great Lakes.

The turbines, more than 400 feet high, will dot an area of about 24 square miles (62 square km), larger than Manhattan, and be visible low on the horizon from parts of Cape Cod. The site is tucked between the mainland of the cape and the islands of Martha’s Vineyard, an exclusive celebrity vacation destination, and Nantucket.

German conglomerate Siemens AG will provide the turbines. Construction is expected to begin before the end of the year, said Jim Gordon, president of Cape Wind Associates. Power generation could begin by 2012.

The decision to approve Cape Wind, subject to certain conditions designed to protect offshore waters from damage and reduce visibility, is expected to face legal challenges, but Salazar said he was confident the approval would stand.

Supporters say wind farms represent a giant push for renewable energy efforts and reducing dependence on foreign oil, and fit well with the Obama administration’s strategy.

“Greenpeace has been campaigning to get the Cape Wind project built for nearly a decade, and today’s victory is worth celebrating. It is long overdue,” said Kert Davies, research director at the environmental group.

YEARS OF REVIEW

Cape Wind was subject to years of environmental review and political maneuvering, including adamant opposition from the late Senator Edward M. Kennedy, whose six-acre (2.4 hectare) family compound in Hyannis Port overlooks Nantucket Sound.

A final ruling was near in 2009, but delayed again after two Wampanoag Indian tribes complained that the giant turbines would disturb spiritual sun greetings and possibly ancestral artifacts and burial grounds on the seabed.

Opponents have deemed the project an eyesore, and raised issues ranging from a detrimental effect on property values in the popular vacation area south of Boston, to possible damage to birds, whales, fishing, aviation, and historic sites.

U.S. Senator Scott Brown, the Republican elected this year to fill Kennedy’s seat, criticized Wednesday’s decision and said the project was a threat to regional tourism and fishing.

The Advisory Council on Historic Preservation, a federal agency in charge of safeguarding historic landmarks, recommended this month that the project be rejected.

The governors of six eastern U.S. states shot back in a letter to Salazar, arguing that other offshore projects will likely be abandoned if the Cape Wind project was rejected.

Salazar cited that letter as part of his decision. “We believe there is huge potential for offshore wind along the Atlantic. We don’t want to be second to anyone,” he said.

U.S. wind generation increased by 27 percent last year, accounting for 2 percent of total electricity supplies, according to the Energy Department. Wind power supports about 85,000 American jobs.

“Renewable energy projects like these not only help fight climate change, they can create jobs and play a central role in our economic recovery,” said Frances Beinecke, president of the Natural Resources Defense Council.

Several countries have achieved much higher levels of wind power generation, often with large government subsidies, including Denmark, Spain and Portugal.

Less than 2 percent of wind energy is offshore, but turbine makers see it as an area of huge growth potential.

Siemens rival General Electric Co expects to increase its offshore business to generate $3 billion to $5 billion a year over the next few years, chief executive Jeff Immelt said at the company’s annual meeting in Houston on Wednesday.

Tom King, president of the power company National Grid US, said talks with Cape Wind about purchasing its output are continuing.