The move means Obama will be at the summit on Dec. 18, considered a crucial period when more leaders will be in attendance, as opposed to his scheduled stop in Denmark on Wednesday on his way to Nobel Peace Prize events in Oslo.
It also means that Obama will be squeezing in a separate, 10th foreign trip before Christmas - a record pace of travel for a first-year president - as a means to giving momentum to a deal aimed at combatting global warming.
Obama will now leave for Oslo late Wednesday, attend Nobel events Thursday and return to Washington on Friday. The official would speak only on condition of anonymity because Obama's plans had not yet been announced.
Obama had said that he would travel to the Copenhagen conference if his appearance would help clinch a deal. His decision to go early to the two-week meeting was looked upon by many as a sign that an agreement was still a long shot.
But now with the U.S., India and China all with specific proposals on the table for the first time, a political agreement seems more likely.
India pledged Thursday to significantly slow the growth of its carbon emissions over the next decade. China announced its own targets for cutting carbon emissions last week, a day after Obama announced the U.S. goals.
None of the three countries - which are among the top five emitters of carbon dioxide in the world - were subject to limits put in place by the 1997 Kyoto Protocol, the treaty that negotiations in Denmark seeks to replace.
The change in Obama's travel plans is a political calculation meant to produce the most possible gain at the summit. Obama has promised aggressive leadership on climate change, so much that it helped win him a surprising Nobel Peace Prize.
Going to Copenhagen during the second week of the summit is the president putting "a little more skin in the game," said MIT management professor John Sterman, an expert in modeling potential greenhouse gas pollution reductions. "The closer to the end of it that he attends, the more he's connected to whatever the outcome is."
The development came one day after India said it would cut the ratio of greenhouse gases pollution to production by 20 to 25 percent from 2005 levels by 2020 but would not agree to hard limit on the amount of heat-trapping gases it could release. India's pledge, like the one made earlier by China, is a cut in carbon intensity.
That means emissions can keep rising as their developing economies grow, but they would do so more slowly. China pledged weeks ago to commit to a 40 to 45 percent reduction in carbon intensity from 2005 levels over the next decade. That means its emissions would grow at half the rate they would otherwise.
By contrast, the U.S. will propose a cut in emissions over the same time period in the range of 17 percent, regardless of the growth of its economy. For the U.S. to achieve the target it proposes, however, Congress will have to pass legislation to curb greenhouse gases blamed for global warming.
The Senate has said it will not take up the measure until next year.
And even if it does, a 17 percent reduction by 2020 is lower than what scientists say is needed to avert the dangerous consequences of climate change.
Scientists say the industrial countries must slash carbon emissions by 25 to 40 percent by 2020 below 1990 levels to prevent the Earth from warming 2 degrees Centigrade (3.6F), the maximum to reduce the worst risks. Obama's proposal - which matches a bill that passed the House in June - translates to a 4 to 5 percent reduction from 1990 levels.
Associated Press writer Seth Borenstein contributed to this report.