Japan's Cabinet has approved a package of economic sanctions against North Korea. The move is not expected to push North Korea to reverse course on its nuclear program.

A North Korean cargo ship, carrying used bicycles on the deck, is berthed at Shimonoseki port in Yamaguchi prefecture, western Japan October 12, 2006

There were 22 North Korean cargo freighters in Japanese ports Friday morning, when Japan imposed new sanctions on Pyongyang, banning North Korean shipping for six months. The ships were given until Saturday to leave, but by Friday evening, all were gone, some without loading or unloading their cargo.

The six-month ban, which also covers all imports of North Korean goods, goes into effect Saturday, as punishment for Pyongyang's announced nuclear test on Monday.

The Finance Ministry is requesting that banks freeze all transactions related to North Korean imports.

North Korea, however, is reliant for the bulk of its international trade on land and air routes with China.

The director of Asian studies at Temple University Japan, professor Jeffrey Kingston, says that means that cutting off the Japanese market will not greatly affect North Korea.

"There's real limits on exactly what Japan can do to harm the North Korean regime," he said. "The people that will get hurt, obviously, are not the leadership."

But Japan's trade minister, Akira Amari, says there is one critical segment of North Korean society that will feel the pain.

Amari says this is the start of the season for matsutake mushrooms, and sales of the delicacy to Japan directly benefit the North Korean military. Thus, he says, the sanctions will have a significant impact.

Two-way trade between the countries, which have no diplomatic relations, had already slowed after North Korea's barrage of missile test launches in July. Japan imposed limited sanctions at that time.

Besides mushrooms, North Korean ships regularly bring clams and sea urchins to Japan. The ships return to North Korea loaded with second-hand appliances, cars, motor scooters and bicycles.

The U.N. Security Council is aiming for a new resolution on Friday calling for sanctions on North Korea. If that passes, Japan is expected to impose another round of measures, including more extensive financial sanctions.