Oct 25 (Reuters) - U.S. power utility Dominion Energy and Spanish turbine maker Siemens Gamesa said on Monday they will build the first U.S. factory to make blades for offshore wind power, part of plans to make a regional supply hub for the industry. Siemens Gamesa (SGREN.MC) and Dominion (D.N) will invest $200 million to build the blade factory in Portsmouth, Virginia, near a marine cargo space Dominion is leasing to build turbines for its project, the Coastal Virginia Offshore Wind project, or CVOW. The factory is expected to be finished around 2025. Dominion hopes CVOW will be the largest U.S. offshore wind farm of 180, 800-feet-tall (245 m) turbines to be installed nearly 30 miles (48 km)off the Virginia coast. CVOW, expected to be finished in 2026 depending on permits, would have a capacity of 2.6 gigawatts, enough to power 660,000 homes. "You"re seeing pieces coming together to not only support our CVOW project but to support the future of offshore wind on the East Coast," said Mark Mitchell, a Dominion senior vice president for project construction. CVOW is undergoing an environmental review by the federal Bureau of Ocean Energy Management, expected to be completed in mid-2023. It also needs approval from Virginia. President Joe Biden has set a goal of 30 gigawatts of offshore wind power by 2030 as part of a plan to decarbonize the power grid by 2035. Dominion is also leading construction of a $500 million ship to build turbines called the Charybdis, the first in the country that will comply with the Jones Act, a century-old law requiring goods moved between U.S. ports to be carried by domestically built vessels. Steve Dayney, head of offshore, North America, for Siemens Gamesa, said the blade factory will support about 260 workers. The factory will supply CVOW with some 500 blades but also look to other projects, much like Siemens Gamesa"s blade factory in Hull, UK, is expanding to become a regional hub. "This is a big step in developing the whole offshore industry and a proof point of all the benefits that offshore can bring to the U.S. as it did ... in other locations, such as Europe or Taiwan," Dayney said. Terry McAuliffe, a Democrat running in the Nov. 2 election for governor, has been supportive of wind power. Glenn Youngkin, a Republican candidate for governor, supports wind power, but has also said it could raise consumer power bills and has criticized the state"s clean energy law. Dayney said Virginia has been a supporter of offshore wind "from the beginning and we trust that all parties are looking forward to making it a success."