With the lowering of giant steel legs to the sea bottom off Rhode Island, construction has officially begun on the country’s first offshore wind farm, starting what U.S. officials hope will be a race to harness a vast energy resource capable of powering millions of homes along the East Coast.

The project developer, Deepwater Wind, marked the “steel-in-the water” milestone for its Block Island Wind Farm on Monday, an event witnessed by federal and state officials who crowded into a boat to view the foundations for two wind-tower platforms jutting above the water.

The farm’s five turbines are expected to begin turning next year, providing electricity for about 17,000 nearby homes while also boosting prospects for planned wind-energy projects from Massachusetts to the Carolinas, or so Obama administration officials hope.

“Block Island Wind Farm will not only tap into the enormous power of the Atlantic’s coastal winds to provide reliable, affordable and clean energy to Rhode Islanders, but will also serve as a beacon for American’s sustainable energy future,” said Interior Secretary Sally Jewell, who traveled to the resort Island for the event.

The project, located in state waters just under three miles from the island’s southeast coast, is being viewed as a hopeful, if modest, new beginning for an industry that has stumbled in recent years, beset by legal battles and financial difficulties. While European and Asian countries have built vast offshore wind farms to convert steady ocean breezes into electricity, no comparable U.S. projects have begun construction until now.

Proposed wind farms in coastal Massachusetts, New Jersey and Delaware have stalled because of problems with financing, regulatory approvals or — in the case of Cape Cod’s Cape Wind Project — opposition from local landowners, including a member of the billionaire Koch family. Wind-energy supporters say a successful first demonstration of the technology could provide momentum for a form of renewable energy that, if fully harnessed, could provide 4,223 gigawatts of electricity, or four times the current capacity of the U.S. electric grid, according to government estimates.

“We hope it jumpstarts offshore wind development along the East Coast,” said Claire Douglass, campaign director at Oceana, a nonprofit that focuses on protection of marine ecosystems. “Once the benefits of offshore wind can be demonstrated on a small scale, the industry can focus on larger projects that will provide more power at lower costs.”

The 30-megawatt Block Island project is backed by a mixture of federal grants and private investment money. Deepwater Wind CEO Jeffrey Grybowski acknowledged that “the world is watching closely what we do here.”

“This moment has been years in the making — and it’s just the start of something very big,” he said.

The construction launch came on a day when the White House announced new commitments from major U.S. corporations in shifting to renewable energy and reducing emissions of carbon pollution blamed for climate change. Thirteen U.S. firms, collectively representing $1.3 trillion in revenue, also expressed support for a strong international accord on climate change during negotiations in Paris late this year.

“We think Paris is a big deal,” said Kevin McKnight, chief sustainability officer for Alcoa, the aluminum giant which announced plans Monday for a 50-percent reduction in the company’s greenhouse gas emissions by 2030. “We think it is critical that the business community gets behind government and ensures that we really do use Paris as an opportunity to move the world in a different direction.”