Japan will continue to urge the United States to ratify a 1997 treaty designed to prevent global warming, even though Washington has announced plans to withdraw from the landmark pact, Chief Cabinet Secretary Yasuo Fukuda said Thursday.

"We believe it is extremely important for the United States, the world's largest emitter of carbon dioxide, to conclude the Kyoto Protocol," the top government spokesman said. "What the Japanese government must do is continue to call on the United States (to ratify the treaty), and keep up diplomatic efforts to ensure the Kyoto Protocol will take effect."

White House spokesman Ari Fleischer told a Wednesday news briefing in Washington that President George W. Bush has instructed his administration to review the U.S. stance on the Kyoto Protocol.

The treaty, negotiated and signed in Kyoto, would require the world's industrial countries to impose binding limits on emissions of heat-trapping gases, which scientists believe are causing significant changes in the Earth's climate.

Under the treaty, the U.S. would have to reduce its emissions of carbon dioxide, methane and certain other pollutants by 7 percent from 1990 levels by 2012.