"For me the first challenge for Cancún is to turn the Copenhagen Accord and turn the other decisions which were near agreement in Copenhagen into a functioning architecture," De Boer said.
Such an agreement, he said, would gather adaptation, mitigation, technology and finance together "into a functioning architecture that really gives developing countries the confidence that it's going to be in their interest to move forward," de Boer said.
"I think it is possible to reach a final agreement in 2011 in South Africa," De Boer argued.
But before a deal is struck, a common understanding is needed on what it would actually mean for an agreement to be legally-binding in nature, the UNFCCC chief stressed. Although the EU and many developing countries insist on the need for a legally-binding agreement, there is little understanding at the moment of what this would mean in practice.
"Is it a treaty that's binding at the international level, is it a treaty that's binding at the national level, or is it a treaty that's binding through the implementation rules that it's given, or is it all three? That needs to be clear first."
De Boer said the EU could play an instrumental role in furthering such debates and driving the negotiations forward.
In his eyes, the EU has not lost leadership on climate change diplomacy despite being sidelined on the final stretch of the Copenhagen negotiations (EurActiv 19/12/09). European leaders, he stressed, made "significant contributions" to getting the final accord signed.
"Europe also made proposals which ultimately didn't make it into the Copenhagen Accord but maybe will make it into a future agreement," he added.
"I think the priority for the EU now is to move its part of the $30 billion short-term finance in a credible way to support the priorities of developing countries," de Boer said.
Financing will be key to bridging the divide between the rich and poor countries, de Boer further stressed. He said that in addition to prompt delivery of fast-start financing, a financial architecture to dispatch the $100 billion pledged by industrialised nations will be needed to reassure the poorest countries that the funds will support their priorities.
"What we should be doing under the context of the [UN Framework Convention on Climate Change] is setting the parameters for finance, identifying the countries that should receive priority support, identifying the issues that should receive priority support, identifying how support should be provided, for example within the context of nationally-approved adaptation and mitigation strategies," the UN climate executive said.
One of the stumbling blocks to agreeing a fully-fledged treaty has been the attitude of the US. The political agenda in Washington has been hijacked by healthcare reform, delaying the passing of climate legislation. De Boer was nevertheless positive about the Obama administration's ability to contribute to the negotiations in Cancún even if there is no domestic legislation in place by then.
"There is a continuous communication between the [US] Administration and the Senate to ensure that whatever is agreed will meet the basic conditions which the Senate has," he said. He stressed the importance of making sure that any agreement struck would subsequently be acceptable to all national parliaments.
"I think it's important to remember that not a single one of the countries that signed up to a target in Kyoto had the national legislation in place," de Boer said, stressing that the UN process has demonstrated its capacity to work.