"The countries (outside the treaty) say they will take measures on their own but I wonder if they can work," Foreign Minister Nobutaka Machimura said.

"We want to continue urging them to join the protocol," he said.

The protocol goes into effect Wednesday for most of the industrialized world which has committed itself to slashing gas emissions.

Notable exceptions, the United States and Australia, have held out saying the harm to their economies from the treaty would be too great.

Fast-growing developing countries China and India are also outside the treaty, which was reached in Japan's ancient capital in 1997 and has been ratified by 141 countries.

Despite Japan's enthusiasm for the treaty, its trade and industry ministry has said 11 of its 30 industries could fail to meet targets aimed at helping the Asian power meet its requirement to slash emissions by six percent from 1990 levels by 2012.

Chief Cabinet Secretary Hiroyuki Hosoda on Tuesday told lawmakers of ruling coalition partner New Komeito that Japan could "narrowly meet" the target.

"But we cannot be optimistic and have to make full efforts," Jiji Press news agency quoted Hosoda as saying.

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