Mr Byers is speaking for the International Climate Change Task Force at the UN summit on the issue.
He said the UK must engage with the US to persuade it to adopt climate change targets once George Bush leaves power.
And the US refusal to agree the Kyoto treaty should not stop other nations agreeing further targets, he said.
Mr Byers argued the US should be encouraged to tackle emissions in other ways before taking on targets at a later date.
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