SYDNEY, Australia — Pacific Rim leaders agreed Saturday to tackle global warming by improving energy use and managing forests better, as thousands of demonstrators rallied to demand the governments do more and act faster.

Some experts and activists dismissed the program adopted by the presidents of the United States, China, Russia and leaders of other Asia-Pacific economies at an annual summit as too modest to be effective. But the program's main backers — Australia and the U.S. — hope to influence upcoming U.N. negotiations on climate change.

"The world needs to slow, stop and then reverse the growth of global greenhouse gas emissions," the 21 leaders said in the Asia Pacific Economic Cooperation forum's Sydney Declaration on Climate Change, Energy Security and Clean Development.

The summit host, Australian Prime Minister John Howard, said its participants had "charted a new international consensus for the region and the world."

"A great challenge for our region is to balance our energy needs with action to address the threat of climate change posed by greenhouse gas emissions," Howard said outside the Sydney Opera House, where the leaders adopted the declaration on the first of two days of talks.

A dozen blocks away and on the other side of a 10-foot metal fence fortified by concrete barriers and a police cordon — about 3,000 protesters held a colorful, mostly peaceful march and rally. Causes included protests against President Bush, the Iraq war and ending poverty.

Kerry Nettle, a senator from the Greens party, demanded that the Pacific Rim leaders take "real action" on global warming, drawing cheers. One protester wore a T-shirt that read "Climate Change is not Cool" while another was dressed as a polar bear.

Police had only minor scuffles with demonstrators.

The APEC climate change program brings together some of the world's powerhouse economies and some of its biggest polluters. As such, the agreement could influence upcoming negotiations before the end of the year in Washington, New York and Indonesia to devise a successor to the U.N.-backed Kyoto Protocol when it expires in 2012.

"If you have APEC, especially the largest emitters — the U.S., China, Russia, Japan — sign up to an agreement like that, it would be hard to ignore at the global level," said Malcolm Cook of Sydney-based think-tank the Lowy Institute.

The program's centerpiece is a goal to reduce "energy intensity" — the amount of energy needed to produce a dollar of gross domestic product — 25 percent by 2030.

The only other concrete goal was to increase forest cover in the region by at least 50 million acres by 2020.