Japan and the United States should draw up contingency and backup plans to secure critical services in case some computer systems do not correctly identify 2000, a senior U.S. government official in charge of millennium bug crisis management said Tuesday.

When computer memories were scarce, computers used only the last two digits of a year to write dates, so many of them are likely to read 2000 as 1900. If not addressed, this problem could have a serious but undetermined impact on social systems.

In his meetings with top Japanese government officials and business leaders the previous day, John Koskinen, chairman of the President's Council on Year 2000 Conversion, said both sides agreed to set up joint working committees in five important areas -- finance, telecommunications, transportation, energy and health. "The major focus was on doing whatever we can jointly to insure that as many systems as possible will be fixed and operate effectively at the end of next year," Koskinen said in a briefing to reporters Tuesday at the U.S. Embassy in Tokyo. "But we also agreed it is clear that in the U.S., Japan and rest of the world, not every system will be fixed," Koskinen admitted.