This is the reason why Obama has changed his participating date at the Copenhagen Summit from December 9 to December 18, as he believes that his negotiations might require a last minute push by world leaders, said Robert Gibbs, White House Press Secretary.

"Based on developments, primarily with the Chinese and the Indians, I think everybody agrees that we are in a better position -- I mean, 'we,' globally -- to get some sort of agreement out of Copenhagen," Gibbs said at a briefing here yesterday.

"The President believed, having helped to work both in enunciating our commitments, as well as ensuring that the Indians and the Chinese talked about their commitments, that we could move that to the end of the conference when some agreement is likely to need some help from world leaders," Gibbs told reporters.

"We announced the trip prior to Oslo, believing that talks in Copenhagen would be good for the President to go and give some momentum to those talks at the beginning of the period in Copenhagen," he said.

When asked about US' commitment in this regard, Gibbs said: "The President continues to strongly believe that the best way forward is through the passage of comprehensive energy legislation, the type of which previously passed the House and is being considered now on the Senate side; that the best way to move forward is through the legislative process, understanding that the Court ruled that some action had to be taken based on the lawsuit."

Meanwhile, Obama today met Nobel Laureate Al Gore, the former Vice-President and a leading advocate of climate change.

Obama, who was earlier scheduled to attend the Copenhagen Summit on December 9, would now be travelling there on December 18 as the White House now believes that there is greater chances of reaching an agreement, mainly because of the new emission cuts targets announced by India and China.

"Based on his conversations with other leaders and the progress that has already been made to give momentum to negotiations, the President believes that continued US leadership can be most productive through his participation at the end of the Copenhagen conference on December 18 rather than on December 9," the White House press secretary said.

"Following bilateral meetings with the President and since the United States announced an emissions reduction target that reflects the progress being made in Congress towards comprehensive energy legislation, China and India have for the first time set targets to reduce their carbon intensity," Gibbs had said last week.