COPENHAGEN - U.N. climate talks are making progress on sharing green technologies but rich nations need to offer deeper cuts in carbon emissions by 2020 to help unlock a deal, the U.N.'s top climate official said on Thursday. There's a general recognition that we need a technology mechanism, as part of a U.N. climate convention, Yvo de Boer told Reuters on the sidelines of December 7-18 talks in Copenhagen, when asked about progress so far.

He said that a U.N. clean technology mechanism would enable rich nations to share solar, hydro or wind power and low-emissions car technology with developing nations. He also told a news conference that good progress was being made on technology.

Developing nations want new technology and billions of dollars in aid to help them move away from fossil fuels, the main source of planet-warming gases, as part of a deal at the end of the Copenhagen talks.

De Boer told Reuters that developed countries would have to deepen planned cuts in emissions to reach a range of 25 to 40 percent below 1990 levels outlined by a U.N. panel of climate scientists to avoid the worst of global warming.

That for me is the goal, de Boer said. Offers so far from rich nations total about 14 to 18 percent below 1990 levels -- emission cuts aimed at slowing warming set to cause more heatwaves, droughts, floods and rising sea levels.

FLEXIBILITY

Many countries have come here with initial offer for targets indicating there is flexibility in the numbers, he said. Whether that is achieved or not depends first of all on a discussion within the group of major developed countries.

Offers include a U.S. target of 17 percent below 2005 levels -- equal to a 3 percent cut from 1990 levels -- and a cut of 20 percent below 1990 levels by the European Union that could be raised to 30 percent if others also act.

But he said it would be hard to satisfy demands by many developing countries for the rich to cut by more than 45 percent by 2020 from 1990 levels -- an amount needed to limit world temperature rises to 1.5 Celsius.

Small island nations such as Tuvalu fear that rising sea levels could wipe them off the map if temperatures rise faster.

That is going to be very difficult, given where emissions are at the moment, to get down to a maximum 1.5 Celsius temperature increase ... It's quite a heavy lift, he said.

De Boer said that it was too early to say whether he felt more or less optimistic about a deal at the Copenhagen meeting.

He said it was counter-productive to make too many judgments while the talks were on-going, comparing that to a cook opening the oven door every 10 minutes to check on a Christmas turkey.

It's not going to do the turkey any good, he said.

(Editing by Robin Pomeroy)

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