The United States for the first time accepted a global commitment to halve greenhouse gas emissions by 2050, diplomats said in Japan.
Attending a Group of Eight (G8) meeting, US President George W Bush agreed that such binding measures should be brought into the United Nations' negotiating framework, which will culminate in a meeting in Copenhagen at the end of 2009, reported dpa.
But the G8 leaders made no progress on medium-term cuts for 2020.