U.N. Secretary General Ban Ki-moon on Friday called on all parties in the U.N. climate change conference here to seal a deal to curb global warming.

The climate talks moved into the final summit segment on Friday, with more than 100 heads of state and government in attendance.

"The purpose of this event is to look beyond Copenhagen," Danish Prime Minister Lars Lokke Rasmussen said in an opening speech.

"We will listen to interventions presenting global perspectives on climate challenges we all face, and we will hear suggestions on how to address these challenges," he added.

Ban called on all parties to be united in action. "It's time for common sense, compromise and courage," he said.

Brazilian President Luiz Inacio Lula da Silva called for the preservation of the principles set in the U.N. Framework Convention on Climate Change and its Kyoto Protocol.

"In any paper that would be passed here in this conference, we would have to keep the principles that were adopted by the Kyoto Protocol and to keep the principles adopted by the convention," Lula said.

"The truth of the matter" was that developed and developing nations had common but differentiated responsibilities, he said.

U.S. President Barrack Obama urged all major economies to put forward decisive national actions on emissions reduction and establish a review mechanism for the actions. He also called for financial support for developing nations to help them adapt to climate change.

The 12-day talks, which began on Dec. 7, have been tasked with sealing a deal to move forward the global fight against climate change after the first commitment period of the Kyoto Protocol ends in 2012.

Negotiators worked overnight on a draft agreement to be adopted at the summit, but hard-fought bargaining continued even when the leaders arrived, with the opening ceremony held nearly two hours behind schedule.

The delay prompted Venezuela's President Hugo Chavez to walk out of the conference room in protest.

Chavez accused U.S. President Barack Obama of arriving late and alleging rich countries had been holding last-minute, secret meetings.