UN chief urges delegates not to duck hard choices as four years of often glacial-paced negotiations reach a peak

* Paris talks on global climate deal resume after one-day break

* Biggest issues unresolved; a "week of compromise" ahead

* U.S.'s Kerry and other ministers to debate finance, measurement

By Bruce Wallace and David Stanway

PARIS, Dec 7 (Reuters) - Organisers of global climate talks in Paris sounded hopeful on Monday that they could reach a deal by the end of the week, even if there was little indication of how differences over funding in particular would be resolved.

"We have to respect the goals we set for ourselves," said French Foreign Minister Laurent Fabius, who is presiding over negotiations that are supposed to conclude with a signed agreement on Dec. 11. "The objectives are clear; the method and the calendar too."

He spoke as senior government ministers, including U.S. Secretary of State John Kerry, began arriving in Paris for the last lap of a four-year process to bind rich and poor countries in a deal to curb greenhouse gas emissions beyond 2020.

It is already certain that the national emissions pledges made ahead of Paris will not be enough to prevent global temperatures rising past a dangerous threshold of 2 degrees Celsius (3.6 Fahrenheit) over pre-industrial times.

But there is at least a growing sense that there will be more money for the developing countries least able to give up fossil fuels to build prosperity, or most vulnerable to the increased floods, droughts, storms and rising sea levels that climate change will bring.

Richer countries are already committed to providing $100 billion a year by 2020; in Paris, the question is how far that annual sum should rise and, most especially, how or whether big emerging economies should contribute.

"I see a growing consensus that $100 billion will be the floor and not the ceiling," said Christiana Figueres, the top U.N. official in Paris.

"Are we there yet, at 100 billion? No," she said. "But we're certainly moving close."

There is also still disagreement on what kind of spending - public or private, new money or old - will count toward that target. Developing nations are resisting attempts by rich countries to fold in existing climate-related spending to reach the $100 billion threshold.

"SYMBOLIC BUT IMPORTANT"

"This $100 billion is a commitment by certain countries that they need to fulfill," said Shri Prakash Javadekar, India's Minister for Environment, Forests and Climate Change.

He said the real cost of the global energy transformation would be in the trillions, but that the $100 billion was "a symbolic but important gesture and one should not run away from it".

Yet on the surface, at least, the conference hosts appear unfazed by such differences.

U.N. Secretary-General Ban Ki-moon opened the second week of talks by telling delegates that "outside these negotiating halls, there is a rising global tide of support for a strong, universal agreement".

He urged the representatives from almost 200 nations not to duck the hard choices as four years of often glacial-paced negotiations peak.

"The world is expecting more from you than half-measures and incremental approaches," Ban told the negotiators, calling for "a transformative agreement".

He said a final deal should include a review of national pledges at five-year intervals, starting before 2020, which some developing nations say is too soon.

He also said the private sector needed to receive a clear signal that the shift to low emissions was "inevitable".

The heavy-lifting in Paris will now be handled by senior ministers with the political clout to make concessions.

"We need to have an agreement somewhat in shape by Thursday if we're going to meet the needs of Friday," Kerry said, after arriving in Paris and meeting with Fabius. "And I think everybody wants to try to get this done."

Fabius, keen to give the impression that momentum toward consensus is growing, has formed working committees headed by a small group of ministers from other countries to tackle the biggest remaining differences.

Among the main issues are "differentiation" (the distinction between rich and poor nations, critical for questions of financing) and "ambition" (how to improve on national efforts in future).

(Reporting by Alister Doyle, Barbara Lewis, Nina Chestney and Lesley Wroughton in Paris; Editing by Kevin Liffey)

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