New York, Sep 22 (DPA) US President Barack Obama Tuesday promised a serious US effort to curb greenhouse-gas emissions that cause climate change and called on all major polluters to make concessions to reach a new global climate treaty.

In a speech at the start of a one-day climate summit at UN headquarters in New York, Obama acknowledged the US has been slow to respond to global warming in the past.

“But this is a new day,” Obama said, noting efforts by his own administration to reduce vehicle emissions and promote renewable energy.

Obama has come under pressure from other countries as major legislation to curb emissions has stalled in the US Senate. But the president insisted the debate has changed in the US.

“We understand the gravity of the climate threat. We are determined to act,” Obama said.

But he also tasked other countries – especially emerging economies like China and India – to make the commitments necessary to lower their own growing emissions, in order to reach agreement on a new global deal by a crucial summit in Copenhagen in December.

“We cannot meet this challenge unless all the largest emitters of greenhouse-gas pollution act together. There is no other way,” Obama said.