The renewal of a Tokyo-Washington agreement on the use of nuclear energy has sparked fears that Japan may take the chance to make nuclear weapons, experts said.

Japan and the United States decided on Wednesday to automatically renew their agreement on peaceful uses of nuclear energy in July when the 30-year pact is due, Japanese media reported.

Japan will be more under the sway of the US after the agreement, which went into effect in 1988, is renewed. The accord, after renewal, can be scrapped in six months if either Japan or the US notifies the other, the Kyodo News said.

The pact lays the foundation for Japan's nuclear fuel cycle project, allowing Japan to extract plutonium and the remaining uranium from spent nuclear fuel and reprocess it into mixed oxide (MOX) fuel for use in nuclear plants.

Japan had tried not to renegotiate the agreement so as to maintain its nuclear fuel cycle policy.

Zhou Yongsheng, a professor of Japanese studies at China Foreign Affairs University, said the renewal means that the Washington administration holds a more tolerant attitude toward Japan's possession of nuclear materials.

"According to its current technology level, Japan certainly has the ability to manufacture nuclear weapons within a short period of time, thus possessing the nuclear materials will undoubtedly add risks to the already unsteady security situation in Northeast Asia," Zhou said.

Japanese Foreign Minister Taro Kono said on a TV program on Jan 11: "Japan needs and has a duty to create a situation in which we can explain with confidence how the country intends to use plutonium to the international community."

Kono is critical of the country's nuclear fuel cycle project.

The Mainichi Shimbun reported that some officials within the US Department of Defense and the State Department's Bureau of International Security and Nonproliferation are concerned about Japan's stockpiling of a massive amount of plutonium, which can be converted into nuclear weapons.

"Japan owns nearly 50 tons of separated plutonium. That is enough for over 5,000 nuclear weapons. Yet Japan has no feasible peaceful use for most of this material," Alan J. Kuperman, associate professor and coordinator of the Nuclear Proliferation Prevention Project, said in a signed article published by Kyodo News on Aug 17.

Kuperman asked how a country that forswears nuclear arms came to possess more weapons-usable plutonium than most countries that have nuclear arsenals.

In their co-authored article published in Japan Times, three US experts concluded that it is undeniable that reactor-grade plutonium－extracted from spent reactor fuel by reprocessing－can be used for nuclear weapons.

They were Victor Gilinsky, program adviser for The Nonproliferation Policy Education Center who served as a Nuclear Regulatory Commissioner under US presidents Gerald Ford, Jimmy Carter and Ronald Reagan; Henry D. Sokolski, the NPEC's Executive Director; and Bruce Goodwin, a Senior Fellow at the Center for Global Security Research at the Lawrence Livermore National Laboratory.