LONDON - Countries should stop blaming each other for the weak outcome of the Copenhagen climate talks and sit down together to move the process forward, the U.N.'s top climate change official said on Wednesday.

It is still possible to reach a legally binding global treaty, and bickering among countries like China and Britain is unproductive, Yvo de Boer, the head of the UN's climate change secretariat, told Reuters.

Britain accused a handful of states including China on Monday of hijacking efforts to agree deep cuts in greenhouse gas emissions. China replied that the allegations were an attempt to sow discord among emerging countries.

These countries have to sit down together next year, so blaming each other for what happened will not help, de Boer said.

The Copenhagen summit ended with a non-binding accord between the U.S., China and other emerging powers that sets a target of limiting global warming to a maximum 2 degrees Celsius and offers funding to help poor nations adapt to climate change, but the details are scant.

It can be an important guiding light or foundation for moving the process forward, and criticizing it or blaming each other for how it came about is not helpful, de Boer said.

A legally binding treaty is still possible and next year should be used to decide its content, which in turn should determine its legal nature.

It's the classical 'form follows function', he added.

Some 28 nations signed the final Copenhagen Accord, but de Boer expects more to step forward and officially support it.

A letter will be going out from the Danish government to all countries informing them of the accord, telling them they have the opportunity to subscribe to it and reminding them of the agreed deadlines.

The accord sets a January 31, 2010 deadline for rich nations to submit economy-wide emissions targets for 2020 and for developing countries to present mitigation actions.

De Boer said subscribing to the accord does not oblige countries to make pledges nor are there penalties for late submissions. Commitments are always warmly received, he said.

UN climate talks will resume in Bonn, Germany in May 2010.

LACK OF UNDERSTANDING

Responding to claims that a few countries had hijacked negotiations in Copenhagen, de Boer said it was a lack of understanding rather than pure objection that prevented delegates from agreeing a robust climate pact.

For developing countries it wasn't clear what a legally binding treaty would mean for them, how it would impact their ability to grow their economies or eradicate poverty, he said.

To commit to a legally binding treaty when you don't know what it means for your country is quite a leap of faith.

De Boer said the countries that denounced the U.S. and China-led plan, including Sudan, Cuba, Venezuela and Bolivia, felt they had not been included in the decision-making process and that they did not have enough time to evaluate the offer.

(The accord) enjoyed very broad support but it didn't enjoy consensus, he said.

De Boer identified four steps which would advance the negotiating process to ensure a comprehensive deal is agreed at next year's UN talks in Mexico:

Taking good stock of Copenhagen, seeing if the accord receives broad support, discussing if a more intensified meeting schedule is needed ... and getting ready for the meetings in May in a solid way.

(Reporting by Michael Szabo; editing by Tim Pearce)