Such legal interpretation can pave the way for expanding the target of MSDF protection to many more non-Japanese ships navigating in the pirate-infested waters off the coast of Somalia.

The inability to protect non-Japanese ships from pirate threats under the existing rules has been a sore point for the Japanese government as it considers ways to contribute to international efforts at combating pirates in the region.

The maritime policing provision in the Self-Defense Forces Law stipulates that the SDF can be authorized to take necessary measures to protect lives and assets at sea, which is generally taken to mean those of Japanese.

In line with this, the government has so far said the MSDF, when providing maritime policing, can protect only Japanese-registered ships and others operated by Japanese firms as well as ships with Japanese people aboard.

According to the lawmakers, who were briefed at a meeting of the ruling bloc's antipiracy project team on Tuesday, government officials told them that it is possible for the MSDF to provide protection to non-Japanese ships as long as they are loaded with Japanese cargo because such cargo can be interpreted to be Japanese assets.

The lawmakers say priority should still be given to Japanese- registered ships and others operated by Japanese firms, partly because the number of MSDF ships that can be deployed on such a mission will be limited anyway.

The project team, set up by the dominant Liberal Democratic Party and its junior partner, the New Komeito party, is considering drafting a bill specifically to enable the dispatch of MSDF ships abroad on antipiracy missions.

The project team is expected to reach a conclusion by around mid-March so the government can submit the bill during the current parliamentary session, but it is also considering deploying the MSDF to waters off the coast of Somalia under the policing provision as a stopgap measure.

Piracy has been rampant in the waters off the coast of Somalia, including the Gulf of Aden, where ships coming to and from the Suez Canal pass through.

A total of 111 piracy incidents took place in the region last year, up from 44 the previous year. Three cases involved ships that were either Japanese-registered or operated by Japanese firms, according to the Foreign Ministry.

Forty-two ships were hijacked last year, and some of them are still being detained, with about 300 crew members held hostage, the ministry said. The bandits are often heavily armed, such as with rockets and automatic rifles.

To combat the pirates, more than a dozen countries, including the United States, European Union nations and China, have sent naval vessels to the waters.

Some of the countries are working to set up a contact group at Washington's initiative to facilitate international coordination on antipiracy efforts in waters around the Horn of Africa nation.