TOKYO: A U.S. nuclear-powered submarine may have leaked a small amount of radiation as it stopped by Japan in the spring and was then deployed throughout the Pacific Ocean, the Japanese government said Saturday.

The Japanese government said that it was informed Friday by the U.S. Navy that the submarine, the USS Houston, may have discharged an amount of radiation that was too small to be considered harmful.

The chief government spokesman, Nobutaka Machimura, said at a news conference that the radioactive amount - estimated at less than half a microcurie - was too insignificant to "affect the human body or the environment."

The submarine spent a week in March in Sasebo, in western Japan, before cruising to Guam and then Hawaii, where the leak was discovered during an inspection late last month, the Japanese government said.

The announcement came as the Japanese government and U.S. military have been trying to ease public resistance to the stationing in September of a nuclear-powered aircraft carrier, the USS George Washington, in Yokokusa, southwest of Tokyo. The scheduled arrival of the George Washington, which will replace the diesel-powered USS Kitty Hawk, has caused protests in Japan, the only country to have been attacked with nuclear weapons.

The announcement also was an embarrassment for the government of Prime Minister Yasuo Fukuda, who reshuffled his cabinet Friday in a bid to raise his low approval ratings. Government officials learned of the leak Saturday from television reports even though the U.S. Navy had informed the Japanese Foreign Ministry a day earlier.

"I, too, came to know about it this morning on television," the foreign minister, Masahiko Komura, said at a news conference Saturday.

Last winter, a Japanese naval warship collided with a fishing boat early one morning, killing its two passengers. But naval officials were criticized for taking more than an hour to inform the defense minister at the time.