UN climate negotiators in Spain are discussing a formula for securing agreement among 192 nations on tackling global warming during a last day of talks before next month's major climate conference in Denmark.

European nations are downplaying expectations for a legal treaty to come out of next month's summit in Copenhagen.

Instead, negotiators are working to hammer out a political agreement that would allow rich nations to make commitments that are not legally binding. The shift follows acknowledgement that several countries, including the United States, may not be politically ready to sign a legal pact by next month.

The head of the UN climate secretariate, Ivo de Boer, says any decision accepted at Copenhagen would be "morally binding."