At the international climate summit meeting in Copenhagen next month, President Obama will tell the delegates that the United States intends to reduce its greenhouse gas emissions “in the range of” 17 percent below 2005 levels by 2020 and 83 percent by 2050, officials said, reflecting the targets specified by legislation that passed the House in June but is stalled in the Senate. Congress has never enacted legislation that includes firm emissions limits or ratified an international global warming agreement with binding targets.

Obama will travel to the United Nations talks to deliver the promise in hopes of spurring significant progress at the summit meeting. He will appear on Dec. 9, near the beginning of the 12-day session, on his way to accept the Nobel Peace Prize in Oslo on Dec. 10, said officials.

By making the pledge in an international forum, Obama is laying a bet that Congress will complete action on a climate bill next year with roughly the same targets and will be prepared to ratify an international agreement based on the commitment.