* Need to be "practical and realistic," Ban says
* UN chief launches "global sustainability" panel
By Patrick Worsnip
UNITED NATIONS, Aug 9 (Reuters) - Secretary-General Ban Ki-moon acknowledged on Monday that a key U.N. conference on climate change in Mexico at the end of this year might not produce the definitive agreement the world body is seeking.
The admission brings Ban, who ultimately is responsible for global climate change negotiations, in line with the view of many national negotiators and some of his own officials.
Attention has focused on the Nov. 29-Dec. 10 meeting in Cancun, Mexico, since a U.N. summit in Copenhagen last December fell short of a legally binding deal to replace the Kyoto Protocol, which expires in 2012.
"We need to be practical and realistic," Ban told a questioner at a monthly news conference at U.N. headquarters on Monday. "It may be the case that we may not be able to have that comprehensive binding agreement in Cancun."
Ban's comment followed a climate meeting in Bonn, Germany, last week where delegates said the talks on pledges to cut greenhouse gases had moved backward rather than forward.
U.N. climate chief Christiana Figueres said at that meeting that goals at Cancun should include a mandate to move toward an all-embracing agreement, "which would take more time." Another focus should be getting countries to deliver on past promises on climate aid and protecting forests, she has said.
Ban said negotiations had made "real progress" in some areas, such as financing poor countries to tackle climate change, developing technology to adapt to it, and reforestation.
"On the basis of these sectoral areas, we will try to build so that we will be able to move ahead in a more comprehensive way," the U.N. chief said. "First and foremost we must bridge the gap of trust between developed and developing countries."
Rich and poor countries are divided over who should bear the brunt of emissions cuts.
The existing agreement caps the carbon dioxide emissions of almost 40 developed countries up to 2012. However, new targets need the agreement of at least 143 countries -- or three quarters of the pact's parties.
At Copenhagen, where Ban had urged the world to "seal the deal" on climate change, most countries signed up for an accord meant to limit a rise in temperatures to below 2 degrees Celsius (3.6 Fahrenheit), but it did not spell out how.
Many rich nations and some major emerging countries such as China, India and Brazil reckon that a legally binding deal may have to wait, perhaps until a further meeting in 2011 in South Africa.
At the request of parties to the Kyoto Protocol, the U.N. climate agency last month detailed contingency plans if the world cannot agree to a successor treaty. These include cutting the number of countries required to approve any new targets or extending existing caps until 2013 or 2014.
Ban on Monday also announced the launch of what he called a high-level panel on global sustainability, to be co-chaired by Finnish President Tarja Halonen and South African President Jacob Zuma and including former Australian Prime Minister Kevin Rudd and U.S. envoy to the United Nations Susan Rice.
He said the panel would study how to lift people out of poverty while respecting and preserving the climate, and would report by the end of next year. (Editing by Eric Beech)