Japan's Lower House of parliament has approved a bill that allows the government to ban the entry of foreign vessels it deems a threat.

The bill mainly targets a controversial North Korean ferry, Mangyeong-bong-92. The North Korean ferry is the only passenger link between the two countries and a vital source of hard currency for the North's impoverished economy.

Japanese authorities suspect that the North Korean cargo-passenger ship may have been used to carry spies and smuggle illegal cargo into Japan.

The bill is expected to be enacted later this month after being approved by parliament's Upper House.

The legislation comes on the heels of new laws that came into force this year, under which Tokyo can impose economic sanctions on the communist North.

But at a summit with North Korean leader Kim Jong-il in Pyongyang last month, Prime Minister Junichiro Koizumi vowed not to invoke sanctions as long as the North respects the Pyongyang Declaration that the two leaders signed two years ago.

Under the Pyongyang Declaration, the two countries agreed to seek a comprehensive solution to North Korea's nuclear and missile programs.