The European Union will work for an "ambitious outcome" at November's climate summit in Cancun, Mexico, and hopes other states will follow suit, climate chief Connie Hedegaard said Thursday.

"We in Europe are ready to do whatever we can to secure an ambitious outcome in Cancun," Hedegaard said during a press conference in Bucharest.

Six months after Copenhagen, where states failed to agree on a binding accord to battle climate change, she said it was more important "to agree on substance first."

"It might be easier afterwards, in South Africa, next year, for instance, to agree on a future legal form," she added.

Hedegaard stressed the EU has so far "delivered" on its promises, but that will not help the world "fix the problem", unless other countries do the same.

"So far we have heard no news coming out from other capitals on the legal form" of an international agreement, she said.

The EU climate chief added the Cancun summit should build on what was agreed in Copenhagen: limiting global temperature increase to two degrees Celsius, helping poor countries cope with climate change impact by providing them 30 billion dollars for the period 2010-2012 and preserving forests.

"This is a set of decisions that need immediate action," she said.