UNITED NATIONS — China laid down a significant plan for curbing greenhouse gases today, outlining ambitious goals of planting enough forest to cover an area the size of Norway and generating 15 percent of its energy needs from renewable sources within a decade.

Chinese President Hu Jintao also promised at the opening of the United Nations climate summit that the communist nation would take "determined and practical steps" to boost its nuclear energy, improve energy efficiency and reduce "by a notable margin" the growth rate of its carbon pollution as measured against economic growth.

Experts were watching the Chinese closely because it had in the past largely ignored global efforts to diminish emissions. The goals Hu outlined also were held in contrast to the United States, where the Senate has yet to take up climate legislation and likely will not have produced a new law by the time world leaders gather this December in Copenhagen, Denmark, to negotiate a treaty to replace the 1997 Kyoto pact.