Good relations between the United States and Japan are more critical now than ever before as the world undergoes dramatic political and economic change, researchers and political heavyweights said.

According to a study Thursday supported by former President Jimmy Carter and former Japanese Prime Minister Yasuhiro Nakasone, the United States and Japan must "foster" a constructive relationship to ensure world order in the 1990s.The United States and Japan account for nearly 40 percent of the world's Gross National Product, and although Washington and Tokyo have recently come together on a number of political and security issues, the bilateral relationship is still troubled by longstanding economic differences.

"Japan's growing economic strength and the continuing imbalances in its economic relations with the United States have tended to nurture an upward spiral of mutual distrust between the two countries," said the report by the Washington think-tank, the Center for Strategic & International Studies.

"If this spiral continues to build and finally precipitates the breakup of the bilateral alliance itself, it will not only be a gravely damaging loss to both countries but may trigger spreading global chaos," the report said.

At a news conference, both Carter and Nakasone noted the importance of the "longterm economic and political alliance" and the idea that the bilateral problems are rooted in economic competitveness rather than cultural disdain.