The bloc, which represents countries vulnerable to climate change, has been adamant that rich nations must commit to emission cuts beyond 2012 under the Kyoto Protocol.
They have been arguing for a "twin track" approach, whereby countries with existing targets under the Kyoto Protocol (all developed nations except the US) stay under that umbrella, with the US and major developing economies making their carbon pledges under a new protocol.
But the EU and the developed world in general has promoted the idea of an entirely new agreement, replacing the protocol.
Talks were halted most of the day, until conference president Connie Hedegaard of Denmark assured developing countries she was not trying to kill the Kyoto Protocol.
The White House said President Barack Obama, who is due to address the conference on Friday, was "committed to pursuing an accord that requires countries to take meaningful steps".
But spokesman Robert Gibbs acknowledged there was a great deal of work to be done.
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