AFP/ Bonn

Key climate negotiations opened in Bonn on Monday with a top UN official warning there was not enough money to host a year-end Paris conference tasked with sealing a global carbon-curbing pact.

Addressing delegates, UN climate chief Christiana Figueres said there was insufficent "funding for participation for either the October session, which is already planned, or for the COP."

She was referring to the next scheduled negotiating round, and to the Conference of Parties, which takes place between November 30 and December 11.

"I regret to inform you that we have a deficit now of 1.2 million euros ($1.3 million) just to cover the sessions you have in your calendar," she said, urging "parties in a position to do so, to contribute."

The hotly-anticipated Paris conference has been charged with concluding a historic pact that will, for the first time, commit all nations to reducing greenhouse gas emissions.

The UN-adopted goal is to limit average global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels.

Diplomats were scheduled to meet in Bonn twice before the year-end UN conference -- on August 31-September 5 and October 19-23 -- to create a workable draft for what will become the Paris pact.