The United Nations climate change summit in Copenhagen was a failure but should serve as a lesson for the future, Russian President Dmitry Medvedev said on Thursday.

"We need to admit that it was a failure... but at the same time it was a lesson. Such events require a different kind of preparation in the future," Medevedev said at a meeting with Russian officials.

He affirmed however that Russia would maintain its previous goal of reducing greenhouse emissions by 25 percent by 2020 relative to 1990 levels.

Medvedev's comments came two months after the Copenhagen summit on climate change, seen even by its supporters as a disappointment and by its critics as a chaotic failure.

Hopes for a binding treaty to halt global warming were dashed when after nearly two weeks of talks, the summit only yielded a general agreement on limiting warming to two degrees Celsius (3.6 degrees Fahrenheit).

The head of the UN's climate change convention, Yan de Boer, announced on Thursday that he was resigning as of July 1.

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