Less than six months after the world agreed to craft a new global climate pact by 2015, talks stumbled at a crucial preparatory meeting Friday as rich and poorer countries butted heads.

With the mood still strained by the fractious 2009 Copenhagen climate summit, negotiations in Bonn showed developed and developing nations split on apportioning responsibility for tackling global warming.

Fast-growing countries like China and India insisted the West, which has been polluting more for longer, must shoulder more of the mitigation burden.

Amid fresh delays and procedural wrangling, UN climate chief Christiana Figueres warned the target of pegging global warming to a manageable 2 degrees Celsius (3.6 degrees Fahrenheit) seemed to be slipping ever further away.

"Current efforts on mitigation are not sufficient, and the doors on improving the probabilities of a maximum two degrees are actually closing in on governments," she said.

It took the 180-odd countries grouped in the former German capital all of 11 days to agree on a work plan for the ADP -- the body that will lead negotiations for a new post-2020 global pact to curb greenhouse-gas emissions.

China and other like-minded countries objected to including pre-2020 emission targets in the ADP's agenda.

"It was not an easy issue to agree," Figueres said, adding that "all parties needed reassurances from each other."

The parties also clashed on a chairperson for the new body, finally thrashing out a consensus agreement at the last minute after interactions that Figueres said had "unsettling echoes".

In the end, the delegates agreed that the candidate of China and most of the Asian Pacific bloc, India, will co-chair the ADP with the West's candidate, Norway, in 2012.

In 2013 and 2014, the co-chairmanships will be held by Trinidad and Tobago, put forward by Latin America and the Caribbean, and a candidate from a developed nation that has yet to be named.

The following year, Africa will co-chair with a developed country.

Expressing relief at the deal, Indian co-chairman Jayant Mauskar said the talks had been "difficult", and Saudi Arabia said it had feared the "dismantling" of the process.

Many delegates expressed anger that the nearly two weeks of talks had been taken up by procedural fights.

"We were disappointed and frustrated that discussions at this meeting focused largely on procedural issues," US negotiator Jonathan Pershing told journalists.

"There is a kind of division in the room, a small group holding up what the rest of the room does," added European Commission chief climate negotiator Arthur Runge-Metzger, saying the group included China.

Denmark's Christian Pilgaard Zinglersen described Bonn as "a lost opportunity".

On Thursday, China rejected accusations by Western delegates that it was holding up progress, insisting it was the United States, Europe and other rich states seeking to "evade legally binding commitments".

But EU climate commissioner Connie Hedegaard said in a statement Friday: "The world cannot afford that a few want to backtrack from what was agreed in Durban only five months ago."

Under the Kyoto Protocol on climate change, whose first leg ends this year, 37 industrial countries are held to specific goals for slashing greenhouse gas emissions.

Poorer countries have no binding targets, but this could change under the deal struck in Durban, South Africa, last year to draw up a new global pact within four years.

"We need to move into a system reflecting modern economic realities," insisted Zinglersen.

China is by far the world's number one carbon emitter and its 1.3 billion people are swiftly getting wealthier, causing the country to burn ever more coal, gas and oil.

On Thursday, German climate researchers said the planet was on a track for warming by more than 3.5 degrees Celsius (6.3 degrees Fahrenheit), boosting the risk of drought, flood and rising seas.

And the International Energy Agency said this week that global emissions have reached their highest ever level.