Ban pleaded with the heads of the European Union (EU), locking horns over a deal for curbing their greenhouse-gas emissions, to demonstrate the leadership for which the world yearned.

"We need a Green New Deal. This is a deal that works for all nations, rich as well as poor," Ban said as 12 days of UN climate talks in Poznan, Poland shifted up a gear with ministerial-level discussions.

"Let us save ourselves from catastrophe and usher in a truly sustainable world," Ban said.

"Today we need global solidarity on climate change, the defining challenge of our era."

Ban argued that "a big part" of the massive stimulus to solve the financial crisis should be devoted to investing in a low carbon economy -- "an investment that fights climate change, creates millions of green jobs and spurs green growth."

The Poznan forum is tasked with advancing towards a new global pact for braking the rise in the greenhouse-gas emissions blamed for damaging the world's climate system.

Negotiations among the 192-member UN Framework Convention on Climate Change (UNFCCC) are mid-way through a two-year "roadmap" set down on the Indonesian island of Bali last year.

The Poznan talks are meant to provide the outlines of a negotiation blueprint. Throughout 2009, further haggling will take place with the aim of fleshing out a deal that can be signed in Copenhagen next December.

But the more than 11,500 delegates in Poland were keeping a worried eye on events in Brussels, where on Thursday and Friday EU leaders faced serious rifts over their own climate pact.

"What we need today is leadership," Ban said. "We look for leadership from the European Union. The decisions currently being made by European leaders in Brussels are [of] great consequences for the whole world."

The EU, credited with salvaging the Kyoto Protocol after the United States refused to ratify it in 2001, has championed demands for a tough post-2012 pact.

Its programme sets down the most ambitious goals of any advanced economy, including 20 percent fewer greenhouse gas emissions by 2020 compared with 1990 levels, increased use of renewable energy sources and overall energy savings.

But Poland, Italy and Germany are demanding concessions, saying the cost of meeting these targets will unleash massive price rises for energy users and burden overheads for important industries.

The envisioned Copenhagen treaty will amount to an action plan for curbing greenhouse gases and channelling help for vulnerable countries beyond 2012, when current provisions expire under the UNFCCC's Kyoto Protocol.

It is designed to be the most complex and far-reaching environment deal ever struck.

It has to be, scientists say.

With rare exceptions, studies say climate change is happening and its eventual impact may be even worse than thought, creating human misery on a massive scale as deserts expand, sea levels rise and extreme weather becomes more and more frequent.

But cobbling together a global deal is a tall order, with the complex discussions in Poznan centered on how to share out the commitments and costs of cutting the carbon pollution that stokes global warming.

Rich countries acknowledge their historic role in pushing up global temperatures but they say emerging powers like China and India must also take action.

Developing and poorer nations hit back with the argument that the industrialised world should lead by example, and foot the bill for clean-energy technology and coping with the impact of global warming.

"There can be no backsliding on our commitments to a future of low-carbon emissions," Ban said. "We must break free of entrenched positions -- who is to blame, who must act first."

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