Japanese Foreign Minister Taro Aso and US Ambassador Thomas Schieffer signed the general security of military information agreement at the Japanese Foreign Ministry.

"It's a great day for Japan and the United States," Schieffer said after the signing ceremony and subsequent talks with Aso, according to Kyodo News.

"We think that this will give Japan and the United States an opportunity to share more intelligence and more information in the future," he said.

The agreement between the two allies follows the revelation of a series of Japan's embarrassing leaks of sensitive information including confidential data on the US-developed high-tech Aegis combat system.

Under the agreement, both governments will restrict the personnel allowed to access secret military information provided by each other.

In an effort to tighten its information control, Japan also established a special division in the foreign ministry to monitor handling of sensitive diplomatic information at the ministry and diplomatic establishments overseas, the government said.

During the meeting with the Japanese foreign minister, Schieffer expressed his hope that Japan will extend the mission in the Indian Ocean, in which Japanese ships provide fuel and other logistical support to US-led forces in Afghanistan.

Officially pacifist Japan approved the mission through special laws passed after the September 11, 2001 attacks to allow participation in the US-led "war on terror." The laws are set to expire on November 1.

Maintaining the coalition in the Indian Ocean "is so important to the security of not only the United States and Japan but to the whole world," Schieffer told reporters.

"We will make our effort to extend the mission, which will be the most sensitive issue in the next parliament session," Aso said, according to a foreign ministry official.

Japan's main opposition leader Ichiro Ozawa, who is savouring a recent election victory to take control of the upper house of parliament, has rejected a personal appeal by the US ambassador to continue supporting military operations in Afghanistan.