President Obama believes US leadership will be key
US President Barack Obama has changed his plans to attend the UN summit on climate change in Copenhagen next week, the White House has announced.
He will arrive later than initially planned, moving his appearance from 9 December to 18 December.
The White House said he believed "that continued US leadership can be most productive through his participation at the end of the Copenhagen conference".
The summit aims to draw up a treaty to succeed the 1997 Kyoto Protocol.
The president had changed his plans after talks with other leaders and after seeing "the progress that has already been made to give momentum to negotiations".
The BBC's Paul Adams in Washington says the White House clearly believes President Obama's presence in Copenhagen, right at the end of the summit, could improve the chances of a deal being struck.
Climate fund support
US representatives will attend the Copenhagen summit throughout negotiations, the White House said.
It said the president believed recent progress included the emissions reduction target announced by the US; China and India setting targets for the first time to reduce their carbon intensity and moves by members of the Commonwealth.
The White House said the president had discussed the state of the negotiations with Australian Prime Minister Kevin Rudd, German Chancellor Angela Merkel, French President Nicolas Sarkozy and British Prime Minister Gordon Brown.
He concluded there appeared to be growing support for the suggested $10bn annual fund to help developing countries deal with climate change.
The White House said the US would pay its "fair share".
"There are still outstanding issues that must be negotiated for an agreement to be reached, but this decision (to delay his arrival) reflects the president's commitment to doing all that he can to pursue a positive outcome," the White House said in a statement.
Mr Brown welcomed Mr Obama's move, a spokesman said.
Danish Prime Minister Lars Lokke Rasmussen echoed Mr Brown.
He said: "President Obama's presence is an expression of the growing political momentum towards sealing an ambitious climate deal in Copenhagen.
Martin Kaiser, Greenpeace International's political climate coordinator, said in a statement: "After a global outcry, President Obama... has come to his senses and accepted the importance of this potentially historic meeting."