"We are aiming at (joint) research to improve the system's missile-detecting and information-processing capabilities," an agency spokesman said.

The agency has asked for 5.5 billion yen (50 million dollars) for the new project in the budget for the next fiscal year starting April 2005, he said.

It was part of an overall budget demand by Japan's defence agency totalling 4.93 trillion yen for the fiscal year.

The Asahi Shimbun newspaper said joint research would focus on developing battle management and command systems as well as semiconductor parts to be used in radars for detecting missiles and planes.

The United States has developed and produced the Aegis system on its own. But the introduction of Japanese civilian-use technology is expected to improve it and enhance missile defence, the paper said.

Japan has four Aegis-equipped destroyers in its fleet. It bought the first one from the United States in 1993.