The Defence Ministry will ask for funds for research and development of ground-based laser weapons in the annual budget request for fiscal 2008, the Mainichi Shimbun daily reported, without clarifying sources.

Developing airborne laser (ABL), or laser weapons installed in an airplane, is included in a longer-term ministry plan, the report added.

The United States called for Japan's cooperation in development of ABL during a meeting on May 1 between US Secretary of State Condoleezza Rice, her Japanese counterpart Taro Aso, US Defense Secretary Robert Gates and Japanese Defence Minister Fumio Kyuma, it said.

Deployment of ABL, however, may breach Japan's pacifist constitution, as ABL is designed to attack enemy missiles immediately after their launches, that could include an offensive in a foreign airspace.

Japanese Prime Minister Shinzo Abe hopes to amend the current constitution, including revising the role of Japanese troops, which now only have defensive capability and are euphemistically called "Self-Defence Forces."

Japan in March deployed its first missile defence system in the Tokyo area one year ahead of schedule as its relations remain tense with nuclear-armed North Korea.

The ministry deployed the launchers, designed to protect the capital Tokyo, earlier than initially scheduled in response to North Korea's launch of missiles in July and its nuclear test in October.

The United States last year installed Japan's first anti-missile system on the southern island of Okinawa, but the interceptors deployed in March were the first installed by Japan on its own.

Two Patriot Advanced Capability-3 (PAC-3) surface-to-air interceptors were installed at the Iruma Air Self-Defence Force base in suburban Tokyo.

Japan has been stepping up its military cooperation with the United States and has vowed to push ahead swiftly with joint missile defenses first prompted by the North's shock firing of a missile over the Japanese mainland in 1998.