Democratic efforts to push a sweeping climate change bill through the Senate this year suffered a severe set-back on Tuesday, when a Republican boycott delayed a key committee’s vote on sending the bill to the full chamber.

The delay nixes any few remaining hopes that the US Congress can pass a bill limiting greenhouse gas emissions before the global climate change meeting in Copenhagen in December. Senate aides are now saying they do not expect the final legislation to even be debated on the Senate floor this year.