The Copenhagen climate summit is a "test of modern leadership" and a failed outcome would almost certainly condemn the planet to disaster, Mikhail Gorbachev said Thursday in an interview.

The Nobel laureate and last leader of the Soviet Union also told AFP that Russia had put forward serious targets for curbing carbon emissions and should not be cast as a spoiler going into the December 7-18 talks.

World leaders faced an unprecedented challenge in forging a lasting solution to global warming and crafting a fair way of coping with its impacts, Gorbachev said by email in response to written questions.

Compromises on policy "virtually guarantee a temperature increase of around four degrees Celsius (7.2 degrees Fahrenheit), well into the catastrophic risk range," he warned.

"The 'business-as-usual' mindset and incremental approach that dominates the world thinking today is the source of our multiple crises -- economic, financial and environmental.

"We are currently in a genuine global emergency that requires a new way of thinking."

Gorbachev argued that a breakthrough was still possible, even if the summit did not yield the legally-binding treaty originally envisioned.

The UN talks have foundered on discord between rich and developing nations over sharing the burden of slashing greenhouse-gas emissions and helping poor countries adapt to climate change.

The first step, Gorbachev suggested, is a "firm political commitment" that spells out the aims and legal framework of an accord that would take effect after 2012.

The meeting would also have to fix a timetable to secure an international binding agreement next year.

"This two-step process should not be seen as a setback but rather a way to strengthen" the deal, Gorbachev said. "Copenhagen thus is a test of modern leadership."

Through his Green Cross International, set up in 1993, Gorbachev has made sustainable development one of his key priorities.

This year, he set up a Climate Change Synergy Task Force, whose members include several top climate scientists and economists, as well as a scattering of former heads of state.

Gorbachev defended the position of Russia, the world's No. 3 polluter.

"Russia is not the bad apple when it comes to climate change," he said, pointing to what he said was an aim to reduce its emissions by 22-25 percent by 2020 over 1990 levels, amounting to a doubling of its previous commitment.

Critics, however, say that the huge drop in carbon pollution after the collapse of the Soviet economy has already helped Russia to meet these targets.

They also note Russia has yet to spell out its proposals in the international arena and has a history of taking a hard line, claiming its vast forests as "carbon sinks" that can be used to reduce its emissions target.

Gorbachev also said that the target of preventing global temperature from climbing more than 2.0 C (3.6 F) -- endorsed by rich nations and emerging giants such as China, Brazil and India -- is not good enough.

"The science says that temperature increase should be limited to around 1.0 C (1.8 F)," he said, calling on developed countries to cut their collective emissions by 45 to 50 percent by 2020.

The offers on the table from rich nations currently totals a cut of about 12 to 16 percent, according to experts.

Asked whether these goals were realistic, Gorbachev was upbeat.

"No one believed in the end of the Cold War at the close of the 1980s... Politics is not about the art of the possible but about making what is perceived as impossible happen."