Indian Prime Minister Manmohan Singh's office announced Saturday that he will attend the U.N. climate change conference which is about to begin in Copenhagen.

India is one of the world's biggest emitters of carbon dioxide - a greenhouse gas blamed for global warming.  The government recently pledged to cut emissions by 20 to 25 percent by 2020, compared to 2005 levels.

Leaders of more than 100 nations are taking part in climate change conference, which aims to reach a new international agreement on reducing emissions and assistance for developing economies working to slow the global warming trend.  

U.S. President Barack Obama, India's prime Minister Singh and most other heads of state or government are expected in the Danish capital during the final sessions of the 12-day conference, which begins Monday.

Mr. Obama has revised his travel plans and will be arriving in Copenhagen for the end of the conference on December 18.  He had originally intended to take part in the meeting's earlier stages, but his spokesman, Robert Gibbs, said the president decided U.S. leadership would be "most productive" during the final rounds of talks.

Thousands of people rallied in London Saturday to demand a strong climate deal at the U.N. conference. 

About 20,000 people turned out for a demonstration organized by the Stop Climate Chaos coalition, which includes groups such as Oxfam and Greenpeace.

Chinese Prime Minister Wen Jiabao, whose country is another major polluter, also will be in Copenhagen.  China, India and the United States all have recently announced their targets for reducing carbon emissions. 

Following India's pledge to cut its greenhouse-gas emissions by 20-25 percent over the next decade, the White House said Friday the United States is ready to pay a "fair share" of $10 billion per year in climate aid to developing countries as part of a new climate change agreement.

Participants in the Copenhagen meetings are trying to reach a new international accord to replace the 1997 Kyoto Protocol, which expires in 2012.

President Obama had originally planned to arrive in Copenhagen on December 9, but his revised schedule calls for him to attend the climate change meetings one week after he accepts the Nobel Peace Prize in Oslo, Norway.

Some information for this report was provided by AP, AFP and Reuters.