United Nations Secretary- General Ban Ki-moon said here Tuesday that at least 90 presidents and prime ministers will be coming to Copenhagen for the UN conference on climate change beginning on Dec. 7.

"Such high-level attendance is a game-changer," Ban said in an address to the Women's International Forum at the UN headquarters in New York, adding he is optimistic about the upcoming crucial UN conference in the Danish capital.

He said in recent weeks, Brazil, Indonesia, Japan, Norway, Russia, the European Union and the Republic of Korea have all stepped forward with new, specific proposals for cutting carbon emissions, Ban said.

The United States and China have agreed to work together and have announced their emission reduction targets, he added.

China announced last week that it was going to reduce the intensity of carbon dioxide emissions per unit of GDP in 2020 by 40 to 45 percent compared with the level of 2005.

Also in last week, the White House said U.S. President Barack Obama would attend the Copenhagen conference and was prepared to put on the table a U.S. emissions reduction target in the range of 17 percent below 2005 levels in 2020.

"From all corners of the globe, we now see unprecedented momentum for governments to act quickly and decisively," Ban said. "I am optimistic Copenhagen can be a success."

The 15th Conference of the Parties of the United Nations Framework Convention on Climate Change (UNFCCC) will be held in Copenhagen from Dec. 7 to 18. Chinese Premier Wen Jiabao will attend the conference.