UNITED NATIONS - Warning that the global economic recession could hinder the ability of countries to take necessary steps to combat climate change, President Barack Obama Tuesday told world leaders “we are determined to act”.

“The journey is hard. And we don’t have much time left to make it,” Obama said in brief remarks at a climate summit convened by US Secretary-General Ban Ki-moon.

The US has put climate at the top of the diplomatic agenda with countries across regions, from China and India to Brazil and Mexico, he said.

Speaking after Ban admonished leaders to put aside differences and move more quickly, Obama sought to show US resolve ahead of crucial talks in Copenhagen in December, when nations will try to reach a new global treaty to address climate change.

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

“We seek sweeping but necessary change in the midst of a global recession, where every nation’s most immediate priority is reviving their economy and putting their people back to work,” Obama said.

He said nations are concerned about reviving their economies amid a global recession, but added that difficulty is no excuse for inaction.

Obama acknowledged that the United States has previously failed to recognize the magnitude of the climate change issue, and he pledged his government’s commitment to developing clean energy sources and reducing greenhouse gas emissions that cause global warming.

President Obama acknowledged that developed nations had caused much of the damage to the global climate, and said they also have the responsibility to lead the global fight against it.

External Affairs Minister S.M. Krishna, representing Prime Minister Manmohan Singh at the summit, is expected to reiterate New Delhi’s stand that any attempt to address the problem of climate change must take into account the imperatives of poverty reduction and economic progress in developing countries and the responsibility of the developed countries.

India maintains that any long-term goal or conditionalities being set towards lessening the effects of climate change “should always take into account the centrality of the need of the developing countries in this regard”.