Basing a U.S. nuclear-powered warship in Japanese waters for the first time will boost stability in East Asia, Japan's government said Friday, hailing an agreement even as it drew protests from the community that will host the aircraft carrier.

The U.S. Navy on Thursday announced the deal, under which Japan — which the United States attacked with two nuclear bombs in World War II — dropped its longtime opposition to hosting a nuclear-powered warship in its territory.

"Japan believes that the continued presence of the U.S. Navy will contribute to safety and stability in Japan, the Far East and the world," Chief Cabinet Secretary Hiroyuki Hosoda said Friday.

He said the agreement would not threaten the safety of Japanese residents, who have long been wary of a U.S. nuclear presence because of fears of radiation leaks.

"The U.S. side has told us that it will continue taking strict safety measures," he said, adding that the carrier — which has not been named — will stop its nuclear reactor while anchored in Japan and conduct no repairs of the reactor there.

The U.S. decided to deploy a Nimitz-class nuclear-powered carrier in Japan because it has far greater capabilities than traditional warships, U.S. Ambassador Thomas Schieffer said Friday at a news conference.

Schieffer said that Washington took into account the reluctance of the Japanese to host a nuclear-powered ship, but such ships are faster and more nimble than fossil fuel powered ships.

"We want to assure all concerned that this carrier can and will be operated safely in Japanese waters," he told reporters at the U.S. Embassy, adding that nuclear-powered ships had made 1,200 visits to Japan over the past 40 years without harming the environment.

The plan immediately met with opposition from local officials south of Tokyo near the city of Yokosuka, home to the U.S. Seventh Fleet and the future base of the new warship.

"No safety tests can be conducted on nuclear-powered ships because Japanese law does not apply, and there is a great risk in the crowded area," said Shigefumi Matsuzawa, the governor of Kanagawa prefecture, where the new warship will be based.

Matsuzawa said he would urge the American and Japanese governments to reconsider the plan.

The nuclear-powered carrier would replace the USS Kitty Hawk, a diesel-powered carrier based in Yokosuka.

The Kitty Hawk, commissioned in 1961, is the Navy's oldest ship in full active service and the only American aircraft carrier permanently deployed abroad. The new carrier would arrive in Japan in 2008, when the Kitty Hawk is scheduled to return to the United States and be decommissioned.

The U.S. Navy said the switch would boost the American military posture in the region.

"Nimitz-class aircraft carriers are far more capable than fossil fuel carriers ... possess superior endurance and sustained speed and can respond more quickly to any crisis," said Rear Adm. James D. Kelly, commander of U.S. Navy Forces Japan.

The announcement came as the United States and Japan worked out a plan for a realignment of the 50,000 American troops based here — a presence that has spurred sporadic protests over the years by residents angered by the crime, crowding and noise associated with the bases.

Earlier this week the two sides struck a deal to close down a Marine Corps air station in Okinawa and transfer its functions to an existing base on the southern island, Camp Schwab. That plan, which calls for the building of a new heliport, was also running into opposition by residents who are against any fresh military construction.

The two sides are meeting for high-level talks in Washington on Saturday to announce an interim plan for realignment. Schieffer on Friday said that the final plan would call for the reduction of U.S. troops in Japan, but he did not elaborate.