The Coast Guard released the radar study earlier this month. After the release of the study, Coast Guard Capt. Raymond Perry called the wind project "doable."
The Coast Guard's recommendations have been issued to the Minerals Management Service.
The Minnesota Democrat, who chairs of the Transportation and Infrastructure Committee which oversees the Coast Guard, said he is also considering holding hearings "to ensure that public and marine safety issues are addressed in the process of permitting (the) offshore alternative energy project."
The plan by Cape Wind Associates would build 130 energy-producing wind turbines in Nantucket Sound. It has been under review by various state and federal agencies since 2001.
Oberstar's letter comes as the Minerals Management Service prepares to release its environmental report on the wind farm at the end of the month.
Barbara Hill, executive director of Clean Power Now, said Oberstar's letter was just a "device to create further obstacles" for the proposal.
"Congressman Oberstar's letter comes at the request of opponents of the project and a number of Massachusetts elected officials who have long used their political clout to fight the wind farm," Hill said in a statement. "Wealthy opponents of the project continue to pull every trick in the book to further delay this important renewable energy project."
But Audra Parker, executive director of the Alliance to Protect Nantucket Sound, a group that opposes the wind farm, said Oberstar's letter was "a necessary step" to protect marine safety.
"We've seen the Minerals Management Service take shortcuts in order to approve this project," said Parker. "This is ensuring us that we have the public comment needed before any decision is made."