Washington, Dec 5 - US President Barack Obama has agreed to attend the last day of the climate change summit in Copenhagen this month in the hopes of hammering out an agreement with other world leaders.

The White House said Friday it now believed his visit would be "most productive" on Dec 18, the final day of the conference, when most other heads of state will be present.

Obama was originally set to join the summit on Wednesday, one day before he receives the Nobel Peace Prize in Oslo.

"There are still outstanding issues that must be negotiated for an agreement to be reached, but this decision reflects the president's commitment to doing all that he can to pursue a positive outcome," White House spokesman Robert Gibbs said.

The summit is aimed at securing an international pact on thereduction of greenhouse gases, but there are still questions about how far industrial nations and major emerging economies are prepared to go to cut their own emissions.  (dpa)