With slim results so far, UN climate talks in Poland enter the home stretch this week haunted by Europe's splintering resolve over its own climate package and the void created by a lame-duck negotiating team from the United States.

Some 10,000 delegates return Tuesday from a two-day break to lay the groundwork for a new global climate pact slated for completion in Copenhagen in December 2009.

Things will shift into high gear with the arrival Thursday of government ministers from more than 150 countries, but the meeting is still likely to spill past its scheduled Friday closure, organisers said.

The urgency of slashing greenhouse gases is not contested: UN scientists have warned that the failure to do so would unleash dreadful consequences for large swathes of humanity within a matter of decades.

But the highly technical negotiations have stalled over how to distribute the commitments and costs of cutting carbon pollution.

Under the United Nations Framework Convention on Climate Change (UNFCCC), rich countries acknowledge their historical role in pushing up global temperatures, but say rapidly emerging economies -- including major CO2 emitters such as China and India -- must also take quantifiable action.

Developing and poorer nations argue the industrialised world should lead by example, and foot the bill for clean-energy technology and coping with global warming's inevitable impacts.

Attempts to construct a climate pact have been made even more difficult by the global economic crisis.

Key to progress thus far has been the EU's ambitious plan to cut CO2 output by 20 percent -- using 1990 as a benchmark -- before 2020, and by 30 percent if others follow suit.

The 27-nation bloc is also shooting, by the same date, for a 20 percent increase in energy efficiency and a 20 percent market share for renewables in the energy sector.

But the plan -- slated for approval at an EU summit at week's end -- has run into stiff resistance from East bloc countries which rely on heavily-polluting coal-fired plants for energy and are demanding concessions.

Even Germany, which spearheaded the EU-wide pact, has recently said its energy-intensive auto and cement industries should be given extra time before being forced to pay for polluting rights.

"If the EU fails to adopt an ambitious package, then its credibility -- when it asks for commitments from others -- will be weakened," commented a non-EU negotiator from Europe.

German Chancellor Angela Merkel and a good part of her cabinet will hold talks in Warsaw Tuesday, with climate high on the agenda.

A hastily convened climate summit Saturday in Poland between French President Nicolas Sarkozy and leaders from nine East European nations failed to smooth over differences.

"We are at a complicated moment," Brice Lalonde, France's climate ambassador, told AFP.

Despite the oft-repeated mantra that the financial crisis will not block progress, "everyone knows that there is going to be less money on the table over the next two years," he said.

The infighting within Europe has already taken a toll on the larger climate debate, some observers said.

"We don't see the same political leadership we saw last year," said Hans Verolme, a consultant for Climate Action Network, a US-based environmental group. "The EU is often simply absent."

Others are looking to the United States to give the process a boost, encouraged by the arrival of President-elect Barack Obama.

But on the ground in Poznan, the United States in still represented by the outgoing administration of George W. Bush, which dealt a nearly fatal blow to climate talks when it ditched the Kyoto Protocol in 2001.

Still, some seasoned negotiators here are confident that Europe will come through -- "even if it is at the last minute," in the words of the non-EU European delegate.

"We all have big expectations of the EU. But I am convinced that the EU is going to solve these internal problems and reaffirm its leadership on the climate issue," he said.

"The problem right now is more a lack of ideas -- nobody has clear ideas."