In Japan, a tireless supporter of the pact, the enactment was being met with a mixture of pride and worry that the world's second-largest economy is unprepared to meet its emissions reduction targets.

The Kyoto targets vary by region: The European Union is committed to cutting emissions to 8 percent below 1990 levels by 2012; the United States agreed to a 7 percent reduction before President Bush denounced the pact in 2001.