The suit by 635 plaintiffs aimed to stop the deepening of the harbor in Yokosuka, site of the U.S. naval base where the nuclear-powered USS George Washington is to be deployed, replacing the aging diesel-powered USS Kitty Hawk.

The carrier has sparked protests among Yokosuka residents who fear it poses a health danger. Many in Japan, the only country to be attacked by nuclear weapons, are also sensitive about any military use of nuclear technology.

Yoshie Ueki, a spokeswoman for the Yokohama District Court, said the court turned down the suit. She did not provide any further information about the case.

The plaintiffs had argued the harbor work, which began last year, would spread pollution, kill fish and damage the livelihoods of fishermen. They also argued the warship would threaten people in surrounding areas with possible radiation leakage should an accident occur.

But presiding Judge Tsuyoshi Ono rejected their claims, saying the harbor work posed no danger to nearby residents, according to Kyodo News agency.

The deployment of the USS George Washington marks the first time a U.S. Navy nuclear-powered vessel will be permanently based in Japan. The move is part of the U.S. military's effort to modernize its forces in East Asia — an area of potential flash points with North Korea or China.

Nuclear-powered warships have visited Japanese ports hundreds of times since 1964, and the United States has provided firm commitments to Tokyo regarding their safe use of Japanese harbors.

The United States has about 50,000 troops stationed in Japan under a mutual security pact.