Amid a national debate over offshore oil drilling, the federal government is preparing to unleash development of another offshore energy source: wind.

The Interior Department, the agency that handles oil-and-gas leases in U.S. waters, is preparing to lease swaths of the outer continental shelf to companies that want to erect massive wind turbines. With the public-comment period for the proposal scheduled to end Monday, competition is heating up to develop wind projects on the shelf, the same underwater formation largely covered...