WASHINGTON — The United States on Nov. 10 designated three sites related to its nuclear weapons program in the 1940s as a national park, stepping up preparations to open it to the public over the next few years.

Some U.S. officials told a designation ceremony that the National Park Service, the operator of the park, will make efforts to assuage concerns in Hiroshima and Nagasaki that it is aimed at justifying the atomic bombings in World War II.

The Department of the Interior, of which the NPS is an agency, and the Department of Energy, which manages nuclear project-related sites, declared the establishment of the Manhattan Project National Historical Park, during a Washington ceremony.

The park consists of three sites in New Mexico, Tennessee and Washington states, parts of which are already open to visitors.

The ceremony took place along with a forum attended by more than 20 experts, including two from Hiroshima and Nagasaki, according to the NPS. Jonathan Jarvis, head of the NPS, told the ceremony, “We will be fair to all, to every community, to every element of the story,” including the impact in Hiroshima and Nagasaki in the planned exhibits at the park.

Secretary of the Interior Sally Jewell said the story that Japan felt the consequences “needs to be told as well.”

The U.S. use of atomic bombs on the two cities in Japan marked the end of the war, “but it left devastation in its wake,” Jewell told participants in the ceremony. Jewell said she heard her mother-in-law, who worked as a nurse in the ravaged cities, had “a powerful experience.”

Vic Knox, a senior NPS official, told reporters the previous day, “This park is not being created to celebrate the creation of the atomic bomb, rather, it is being created to remember and learn from this event which changed the history of the world.”

The three-site park has facilities and land in Los Alamos, the nerve center of the Manhattan Project, Oak Ridge, where uranium was produced for the atomic bomb dropped on Hiroshima, and Hanford, where plutonium was produced for the atomic bomb dropped on Nagasaki.

The NPS has been making preparations to establish the Manhattan Project park since President Barack Obama signed a relevant bill last year.

The cities in western and southwestern Japan were devastated by the atomic bombs the United States dropped on Aug. 6 and 9, 1945, respectively, with around 210,000 people estimated to have died by the end of that year.