Controversial climate change legislation will not move out of a key Senate committee until September, after lawmakers return from their summer recess, according to U.S. Senator Barbara Boxer.

Two days after the Senate Environment and Public Works Committee opened hearings aimed at quick passage of climate legislation, Senator Boxer,a California Democrat, said she has changed the target date for mark up of the bill from August 7 to sometime in early September. The bill is expected to parallel legislation approved by the House June 26, which would place a cap on greenhouse gas emissions that contribute to global warming and create a system for trading in permits to emit the heat-trapping gases.

The intention is to have a bill in front of President Obama by December, when world leaders will meet in Copenhagen to finalize a global deal curbing greenhouse gas emissions that will take effect after the Kyoto Protocol expires in 2012.