Japan and South Korea signed a bilateral treaty Friday to facilitate and speed up their cooperation on criminal investigations, government officials said.

Foreign Minister Taro Aso and South Korean Ambassador Ra Jong Yil signed the pact in Tokyo to enable law enforcement authorities of the two countries to directly interact without going through diplomatic channels.

The Japanese government hopes the Diet will ratify the pact during the 150-day regular session that began Friday, the officials said.

Under the treaty, the justice minister and the National Public Safety Commission and South Korea's justice minister will contact each other when the need arises for investigative cooperation, including requests for information or to question suspects.

Prime Minister Junichiro Koizumi and South Korean President Roh Moo Hyun agreed to launch negotiations on formulating the treaty in a meeting on Cheju, South Korea, in July 2004.

In the five years to 2004, the National Police Agency and the Justice Ministry requested investigative cooperation through diplomatic channels with the United States in 43 cases, with South Korea in 27 cases and with China in 14 cases, the officials said.

The Diet in 2004 ratified a similar treaty Japan has signed with the United States but the U.S. Congress has not ratified it.

Japan has been in preliminary talks with China since June to work out such a treaty.