Federal aviation officials issued a report today finding that the Cape Wind project, which calls for erecting 130 wind turbines in Nantucket Sound, would pose a "presumed hazard" for airplanes because of interference with air traffic control radar systems.

"Initial findings of this study indicate that the structure as described exceeds obstruction standards and/or would have an adverse physical or electromagnetic interference effect," the Federal Aviation Administration said in the report.

But the agency also opened the door to a solution for Cape Wind, suggesting that improvements to one of the three air traffic control radar systems that cover Nantucket Sound could solve the problems caused by the 440-foot-tall wind turbines.

The agency said an upgrade to the radar facility at Otis Air Force Base that would cost about $1.7 million might help. If that fails, then a completely new system at Otis that would cost $12 million to $15 million would be needed, it said.

Mark Rodgers, spokesman for Cape Wind, had no comment on whether the company would be willing to pay for the new equipment.

"We are going to sit down with the FAA and work with them and arrive at a win-win solution that is satisfactory to them and will allow the project to proceed," he said.

Rodgers said the company still believed that it would have all the necessary permits by the end of spring, including the FAA approval.

Opponents of the project said the report showed the project posed significant safety hazards. "It's another reason the project shouldn't be built in that location," said Audra Parker, a spokeswoman for the Alliance to Protect Nantucket Sound, noting that 400,000 flights cross Nantucket Sound every year. "We support renewable energy, but it has to be properly sited."

The FAA is accepting public comment on its report until March 22. An agency spokesman didn't immediately return a message seeking comment.

The lead federal agency reviewing the $1 billion project, the Minerals Management Service, concluded last month that the nation's first offshore wind farm would have no major adverse effect on the environment. The next step is for new Interior Secretary Ken Salazar to decide whether to award Cape Wind a lease for the project.

No matter what he decides, Cape Wind's opponents, concerned about navigational hazards, property values, scenic vistas, and historical sites, have promised lawsuits.