WASHINGTON (Reuters) - A congressionally-appointed panel on Wednesday called for the creation of a U.S. museum of women's history, with preferred sites on or near Washington's National Mall.

The American Museum of Women's History would close a gap in the U.S. capital, which has museums devoted to everything from space and spies to stamps and black history, but none focused on women, its backers said.

"America needs and deserves a physical national museum dedicated to showcasing the historical experiences and impact of women in this country," said the report from the seven-member commission - all women - empaneled by Congress in 2014.

Creation of the museum would call for a decade-long effort to gather support and funding and to build it. The cost for a building of 75,000 square feet (6,900 square meters) to 90,000 square feet (8,400 square meters) would be estimated at $150 million to $180 million in private funds, the report said.

The commission also recommended that Congress donate land free of charge for the museum site or provide an existing building.

The museum would become part of the Smithsonian Institution, the world's biggest museum complex, overseen by a board also appointed by Congress. The federal government would assume operation and maintenance costs.

The panel recommended three sites for a women's museum on or around the National Mall, a vast area stretching two miles (3.2 km) from the U.S. Capitol west to the Lincoln Memorial and often called "America's front lawn."

One site is on the side of the Mall opposite the National Museum of African American History and Culture, which opened in September.

The second site is the Smithsonian's 19th-century Arts and Industries Building, also on the Mall, and the third is on the grounds of the U.S. Capitol.

Congress declared the Mall closed to new building in 2003, but made an exception for the African American museum. With the Mall already crowded with monuments and museums, Washington planners are looking for ways to pay tribute to U.S. historical figures and events away from the area.

(Reporting by Ian Simpson, editing by G Crosse)