US President Barack Obama would attend the Copenhagen summit on climate change at the end of the meeting instead of the beginning as originally planned, the White House announced Friday.

"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 said in a statement.

Last month, Obama announced a 17-percent reduction target of its greenhouse gas emissions below 2005 levels by 2020, which is about 4 percent emissions cut below 1990 levels. This reduction rate is about half of the requirement of the Kyoto Protocol, which the United States has refused to ratify.

Obama was originally scheduled to be in Copenhagen on December 9 before heading to Oslo to accept his Nobel Peace Prize, which some analysts said was surprising as hard talks are likely to take place at the end of the summit when more leaders will be there.

The White House said progress has been made in recent months toward a meaningful agreement on dealing with climate change.

"After months of diplomatic activity, there is progress being made towards a meaningful Copenhagen accord in which all countries pledge to take action against the global threat of climate change," said the statement.

The Copenhagen climate summit is scheduled for December 7 to December 18, where representatives of about 190 countries are expected to renew green house gas emissions reduction targets set by the Kyoto Protocol, the first commitment period of which is to expire in 2012. It is also expected to outline the post-2012 negotiation path.

Janos Pasztor, director of the UN secretary-general's Climate Change Support team, said Friday that there have been "several signs of optimism" recently with over 100 world leaders and 15,000people expected to attend the climate talks in Copenhagen.

Welcoming the recent goal by Obama to cut greenhouse gas emissions and his participation in the conference, Pasztor said UN Secretary-General Ban Ki-moon "believes that the full engagement of the United States in the multilateral process can help propel global action."

"Head of state involvement is crucial for successful outcome in Copenhagen," Pasztor added.

The European Union has committed to voluntarily reducing its emissions by at least 20 percent by 2020, compared with 1990 levels. The new government in Tokyo has pledged to reduce Japan's emissions by 25 percent by 2020 on the 1990 level, if other countries make similar commitments.

However, scientists believe that developed countries should slash their emissions by at least 40 percent against 1990 levels by 2020 in order to prevent global warming from becoming disastrous.

In the Friday statement, the White House also said the United States will pay a "fair share" of the proposed US$10 billion in annual aid to help developing countries cope with climate change.

"There appears to be an emerging consensus that a core element of the Copenhagen accord should be to mobilize US$10 billion a year by 2012" to support adaptation and mitigation in developing countries, particularly the most vulnerable and least developed countries that could be destabilized by the impacts of climate change, the White House said.

"The United States will pay its fair share of that amount and other countries will make substantial commitments as well," the statement said.

(Xinhua News Agency December 5, 2009)