The attacks in Paris are affecting crucial climate change talks in the French capital starting later this month, but more than 120 world leaders strongly support the conference and have confirmed they will attend, a senior UN official said Friday.

Janos Pasztor, the UN assistant secretary-general for climate change, told a news conference that preparations and some activities are affected, including a huge march on Nov. 29 by supporters of an agreement to reduce carbon emissions that has been cancelled by the French government.

However, Pasztor said dozens of leaders still plan to attend.

"They think this is an important event," he said. "So they are putting their travel plans where their mouth is and they will be there to support the climate negotiations."

Pasztor expressed hope that leaders will still heed the voices of the supporters who will now be holding marches in over 2,000 cities and towns around the world during the weekend of Nov. 29.

At the same time, he said, a huge number of climate-related events are being organized in Paris outside the centre where the conference will take place.

"Inevitably, where there's a situation where there's a state of emergency, there will be some impacts on those -- but still the events are going ahead and there's been a very strong sense both from Paris itself and the eventual participants that people intend to go to those meetings and intend to show solidarity with France and participate," Pasztor said.

"So the conference is going ahead and all the related events are going ahead," he said. "That's the bottom line."

World governments are meeting to craft a new UN pact to rein in greenhouse gas emissions.

While it's inevitable that leaders will discuss the co-ordinated attacks in Paris last Friday claimed by the Islamic State extremist group that killed 130 people, Pasztor said he expects their main focus to be on reaching an agreement, which all governments want.

Pasztor said 171 countries that collectively account for more than 90 per cent of emissions -- including top polluters China, the United States, the European Union and India -- have submitted national climate plans with targets.

"If successfully implemented, these national plans bend the emission curve down to a projected global temperature rise of approximately 2 degrees Celsius by the end of the century," he said. "While this is significant progress, it is still not enough."

"The challenge now is to move much further and faster to reduce global emissions so we can keep the global temperature rise to below 2 degrees Celsius," Pasztor said.

He stressed that the Paris conference "must mark the floor, not the ceiling of our ambition."

Pasztor said UN Secretary-General Ban Ki-moon met with leaders from the Group of 20 rich and developing nations last weekend, will meet Southeast Asian leaders this week and heads of state and government from the Commonwealth next week "to help unblock progress on several sticking points" in the hoped-for agreement.