Barack Obama has bowed to international appeals for America to demonstrate commitment to action on global warming, and said he will join other world leaders for the crunch negotiating sessions of the Copenhagen climate change summit.

The White House, in a statement from the press secretary, Robert Gibbs, last night said Obama would adjust his original travel schedule, under which he would have dropped in on the summit on 9 December, en route to receiving his Nobel peace prize in Oslo.

"The president believes that continued US leadership can be most productive through his participation at the end of the Copenhagen conference on December 18th," the statement said. "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 he can to pursue a positive outcome."

The decision avoids a potentially awkward situation which would have seen Obama arrive in Copenhagen a ahead of even senior negotiators or ministers, let alone prime ministers and heads of state. The timing would have created an embarrassing American absence on the last day of negotiations which nearly 100 other world leaders are expected to attend.

The US otherwise was planning to put on a major presence at Copenhagen, with appearances from half a dozen cabinet secretaries and senior officials.

The new schedule for Obama reinforces a building sense of optimism in recent days after the biggest emitters, the US and China, agreed for the first time to some action on global warming. The White House said last week that Obama would call for cutting US emissions by 17% from 2005 levels – far less than the levels dictated by the science, but welcomed by negotiators as a good first step.

In its statement last night, the White House acknowledged that world leaders, including Gordon Brown, the German chancellor, Angela Merkel, the French president, Nicolas Sarkozy, and the Australian prime minister, Kevin Rudd, had spoken about the summit with Obama this week.

Sarkozy, in comments to reporters at the Commonwealth talks in Trinidad last week, was especially blunt – accusing Obama of disrupting the summit.

"We can't allow the presence of one single head of state to stymie the world's affairs," Sarkozy told reporters. "The decisive moment is December 17 and 18. If some come at the beginning and others at the end, when will we be able to take decisions?" he asked.