From a 2005 baseline, a 17 percent emissions cut would fall short of what's needed to keep global warming to 3.6 degrees F. But it may reflect most that US Senate would OK from climate talks.
A European Union agreement last week was short on specifics. US commitments on reductions may not be forthcoming, making Chinese commitments also unlikely.
China is due to unveil a new proposal at the gathering Tuesday, but its plans to cut "carbon intensity" rather than limit emissions may not satisfy US lawmakers.
Obama pledged to tackle global warming in his presidential campaign. Now the world waits to see if he takes a leadership role at a climate change meeting at the UN Tuesday.
This week, negotiators from 182 countries meet in Bonn, Germany to lay the groundwork for a post-Kyoto climate regime.
The UN's top climate official defended a global trading scheme to reduce greenhouse gas emissions after the US government released a report questioning its efficacy.
Talks start Monday in Poland for a post-Kyoto climate treaty.
Researchers track China’s plume of pollution. What effect did Olympic hiatus have?
Its support for halving emissions by 2050 is seen as useful for future negotiations.