Asked about those comments at the time, former UNFCCC Executive Secretary Yvo de Boer offered a conciliatory response.

FORBES: UN Climate Chief Dismisses US Threat To Abandon Negotiations

Yvo de Boer, executive secretary of the UN climate change convention, predicted that the negotiations would get back on track in the early afternoon.

BBC: Copenhagen climate summit negotiations 'suspended'

Ms Figueres, a Costa Rican diplomat and 15-year veteran of the UN climate process, takes over from the current UNFCCC executive secretary Yvo de Boer early next month.

BBC: New UN climate chief calls for more ambition

"This is a sign of developed countries' resolve and courage that the world has been waiting for in Poznan, " said Yvo de Boer, executive secretary of the UN climate convention.

BBC: Gore's tough message to leaders

"The U.S. commitment to specific, mid-term emission cut targets and China's commitment to specific action on energy efficiency can unlock two of the last doors to a comprehensive agreement, " Yvo de Boer said.

CNN: China's premier to join Obama at climate-change summit

On the business side, consultancy firm KPMG - in the shape of its special global adviser Yvo de Boer, former head of the UN climate convention - has highlighted the pledges of the private sector.

BBC: Rio revisited: Glass half-full?