US President Barack Obama tells a UN climate change meeting in New York that the problem is growing faster than the world's efforts to address it.
The world's children in the world should not be subjected to a future beyond their capacity to fix, he said.
It is the biggest high-level gathering to discuss climate change since 2009.
The aim of the meeting is to galvanise 120 member states to sign up to a comprehensive new global climate agreement at talks in Paris next year.
"There should be no question that the United States of America is stepping up to the plate," Mr Obama said.
"We recognise our role in creating this problem, we embrace our responsibility to combat it.
"We will do our part and we will help developing nations do theirs; but we can only succeed in combating climate change if we are joined in this effort by every nation - developed and developing alike."
His goal was to underline that carbon dioxide is damaging to humans in the same way as air pollution, and in the US it should be regulated by executive power rather than by through legislation in a very divided Congress.
The president also acknowledged the scale of opposition to his attempts to cut carbon, but said he was determined to push through. The most substantial pledge he made was an announcement that early next year he would publish a post-2020 plan to cut emissions.