"Clearly it now depends on us, on Germany and Europe, to be ambitious there and not to put the success of Copenhagen in doubt," Merkel told reporters.
"Success means setting clear objectives so that during next year, better in the first half than in the second, we get a legally binding deal as a successor to the Kyoto Protocol."
Merkel said she would discuss Copenhagen on Thursday with French President Nicolas Sarkozy and with the Swedish EU presidency ahead of a summit of the 27-nation bloc "to make our position clear in Brussels."
"Europe is at the forefront here, and is determined not to give ground on ensuring that Copenhagen has to be a success," she said.
Hopes have been dashed in recent weeks that the December 7-18 UN talks would result in a binding agreement on cutting emissions and giving poor countries access to green technologies and to cope with the ravages of climate change.
Instead the 192 countries attending are set to push for a political deal to prepare the way for a binding pact next year to follow on from the Kyoto Protocol, which expires in 2012.