Updated

President Barack Obama delayed his scheduled departure from climate talks here to oversee ratification of a "legally non-binding" agreement pledging green house gas emission cuts sufficient to prevent global temperature increases of no more than 2 degrees centigrade by 2020, a senior administration official told Fox.

Another senior administration official offers the following on the deal:

"Today, following a multilateral meeting between President Obama, Premier Wen Jiabao, Prime Minister Manmohan Singh, President Lula da Silva and President Jacob Zuma a meaningful agreement was reached. Its not sufficient to combat the threat of climate change but its an important first step."

We entered this negotiation at a time when there were significant differences between countries. Developed and developing countries have now agreed to listing their national actions and commitments, a finance mechanism, to set a mitigation target of two degrees Celsius and to provide information on the implementation of their actions through national communications, with provisions for international consultations and analysis under clearly defined guidelines.

No country is entirely satisfied with each element but this is a meaningful and historic step forward and a foundation from which to make further progress.

We thank the emerging economies for their voluntary actions and especially appreciate the work and leadership of the Europeans in this effort."

Details remain fluid about how much and how rapidly developed and developing nations would seek to reduce their own carbon-based pollution. Enforcement and verification measures are equally unclear.

But the senior official confirmed a final text was being prepared for final review. A core group of top economic nations - including the US, European nations and others unknown - are due to vote informally on the text before presenting it to the full plenary session of 193 represented nations gathered here for the most intensive global pollution talks in history.

The senior official was unclear if nations here would commit to pursuing a legally binding climate change treaty in 2010. The most recent text dropped that provision in a sign that many countries here fear they cannot muster the political will to translate pledges into concrete action.

Much remains uncertain about how credible the pollution reductions will be and how rapidly developing nations will "mobilize" aid to developing countries to speed up their pollution-cutting efforts.

Obama will leave by 11 pm Copenhagen time for the return flight to DC. He will meet with reporters before departing to comment on the climate deal.