The United Nations says China has taken the lead in tackling climate change, but Canadian Environment Minister Jim Prentice says the Chinese government has yet to set firm goals for cutting greenhouse gas emissions.

Chinese President Hu Jintao pledged at the UN Climate Change Summit in New York that his country would plant enough trees to cover an area the size of Norway, cut its dependence on non-renewable energy, and reduce its carbon pollution.

"At stake in the fight against climate change are the common interests of the entire world," Hu said. "Out of a sense of responsibility to its own people and people across the world, China fully appreciates the importance and urgency of addressing climate change."

Both Hu and U.S. President Barack Obama spoke at the summit, and were among 100 leaders gathered in New York.

Obama spelled out his country's commitment to the global climate change fight and the challenges that lie ahead.

"We understand the gravity of the climate threat, we are determined to act and we will meet our responsibility to future generations," he said.

Obama also called on the world's nations -- both rich and poor alike -- to be a part of the solution.

"After too many years of denial, we finally know what needs to be done," he said.

Prime Minister Stephen Harper was not at the summit, but asked Prentice to attend in his place. However, Harper was in New York and met with Mayor Michael Bloomberg for about half an hour.

The two leaders talked trade issues and Harper invited Bloomberg to the 2010 Olympic Games.

Harper did talk briefly about climate change and blamed the previous Liberal government for Canada's lack of action.

"Canada's come a long way from where we were," Harper said Tuesday outside New York's City Hall. "The previous government signed an international climate-change agreement and decided they wouldn't implement it."

But Harper also attended a leader's dinner, drawing criticism for his no-show for the climate change proceedings.

"I don't know why he has time to attend a fancy dinner and doesn't have time to go to the floor of the General Assembly and put (forth) Canada's position," Liberal environment critic David McGuinty said.

Prentice on China

Speaking to reporters, Prentice questioned whether China's commitments had any substance. Both China and the U.S. never signed on to the Kyoto Protocol, unlike Canada, although the Harper government has said it cannot meet its Kyoto targets for reducing greenhouse gasses.

"The Chinese President made a historic speech ... but did not offer binding targets in terms of reductions, but rather targets that are related to specific things that would be done in China relative to energy efficiency, renewable energies and so on," Prentice said.

However, earlier this week, Yvo de Boer, the UN climate chief, said China is becoming an undisputed global leader in the fight against climate change.

"China and India have announced very ambitious national climate change plans. In the case of China, so ambitious that it could well become the front-runner in the fight to address climate change," de Boer said Monday. "The big question mark is the U.S."

Tuesday's summit was seen as a way for countries to find common ground on climate change, prior to a critical and upcoming summit in Copenhagen, Denmark.

The Copenhagen talks will see nations working towards forming a new global climate pact that will replace the 1997 Kyoto Protocol that expires at the end of 2012.

Kyoto ending

The Kyoto Protocol bound 37 industrial countries to reduce their greenhouse gas emissions by 5.2 per cent of their 1990 levels. The 1997 pact gave the countries until 2012 to meet their targets.

Developing countries were not obliged to follow the presumed lead of industrial nations when Kyoto was signed 12 years ago. This time around, there will be higher expectations for them, as any changes that are agreed to will affect billions of people, businesses, farms and households around the world.

CTV's Ottawa Bureau Chief, Robert Fife, said the tension between the United States and China, as well as India, concerns all the countries taking part in the Copenhagen talks later this year.

"The Americans, under President Barack Obama, want a treaty, but not unless the other big emitters also sign on," he told CTV News Channel during a telephone interview from New York.

Fife said the U.S. also prefers getting a treaty signed that will not bind them to international targets, if possible.

With less than 90 days until Copenhagen, Prentice admitted that "there is a lot of work to be done."

"People are working hard though, and we continue to be hopeful," he said.

In any case, Prentice said that the international community wants "to get to a treaty that actually works."

"But it can only work if the people who emit carbon are governed by the treaty," Prentice said. "And that's why for China, India, Brazil, it's central in our Canadian position that they have targets under the Copenhagen agreement and that the United States agree and ratify."

He later told CTV's Power Play that Canada will work closely with the U.S., likely to create a harmonized plan -- one that works with the two countries' linked economies.

But McGuinty and NDP environment critic Linda Duncan slammed Prentice, saying Canada had been reduced to a bystander at the UN. They said while other countries have tried to negotiate tougher environmental goals, Canada has waited for the U.S.

"We're basically non-players," said McGuinty. "We have vacated our international goals, or international responsibilities."

With files from The Associated Press and The Canadian Press