The EU will fight to the last for credible commitments at the Rio+20 Earth summit but it will be "very very difficult", the bloc's environment commissioner Janez Potocnik said Wednesday.

The European Union will "engage till the very last moment and we are going there exactly with that commitment," Potocnik said, citing "optimism" but admitting there were no guarantees of an all-encompassing agreement.

"After tough pre-negotiations in New York, unfortunately not enough progress has been made so we have some intense days ahead of us in Rio," the commissioner said.

Privately, EU negotiators were more forthright. "It will be very, very difficult to draw up concrete measures and fix dates," one told AFP.

"No promises were made during lead-up negotiations," said another. "There was nothing concrete, just a lot of blah-blah-blah and statements of intention."

French dreams of creating a World Environment Organisation, for instance, are not expected to see the light of day. "At best there'll be a bigger role for the United Nations Environment Programme (UNEP)," said a senior European official.

The presidential election campaign in the United States is one factor, with US President Barack Obama skipping the summit and Congress unlikely to ratify whatsoever.

Chinese refusal to act in the absence of Washington is another, the negotiator added.

Secretary of State Hillary Clinton heads to Rio de Janeiro for the June 20-22 conference, the Earth Summit's 20-year follow-up, which is drawing wide global participation.

The landmark 1992 summit, where then US senator Al Gore played a high-profile role, set the ball rolling in UN-led efforts to tackle problems facing the planet including climate change and species loss.

But Potocnik said he viewed the summit as the launch of a process, with much to be done in its wake.

"For success in Rio the adoption of a document with concrete targets is enough," he said.

"As long as we agree on things we think need to be done," Potocnik said.

"We might not achieve all targets in all areas but even if we come to a partial achievement I will be quite happy," he said.

Potocnik said that with 130 heads of state and government due to show, "we should all go there, at whatever level, with an understanding we need that agreement for a better future."

"Concerning the EU, I'm optimistic we will speak with one voice strongly," he said. "My call would be that simply dispersing our message would simply not help."

As many as 50,000 activists, policymakers and business executives are expected for the 20-year follow-up. But expectations for major achievements are low as much of the world focuses on present economic woes.

The EU is also sending three other commissioners: Connie Hedegaard, responsible for climate action; Dacian Ciolos, who holds the agriculture portfolio; and development chief Andris Piebalgs.

Commission president Jose Manuel Barroso may also attend, if the eurozone crisis permits.

UN environment summit opens, but prospects grim
Rio De Janeiro (AFP) June 13, 2012 - Twenty years after the first Earth Summit, a renewed bid to rally the world behind a common environmental blueprint opened Wednesday in Rio de Janeiro against a backdrop of discord and economic gloom.

Kicking off the so-called Rio+20 summit, Dilma Rousseff, president of host nation Brazil, called on "all countries of the world to commit" to reaching an accord that addresses the most pressing environmental and social woes.

The UN conference, which marks the 20th anniversary of the Earth Summit -- a landmark 1992 gathering that opened the debate on the future of the planet and its resources -- is the largest ever organized, with 50,000 delegates.

Around 115 leaders are expected to attend the main event itself on June 20-22 but a series of conferences grouping businesses, environmental groups and non-governmental organizations are being held in advance.

This frenzy of contacts and deal-making could well be more fruitful than the UN Conference on Sustainable Development itself, analysts say, mindful of the failures of the 2009 climate summit in Copenhagen.

Behind the scenes, there is incipient panic over the draft summit communique after three rounds of preliminary informal negotiations left more than 75 percent of the paragraphs still to be agreed.

The charter is supposed to sum up the challenges and spell out pledges to nurture the oceans, roll back climate change, promote clean growth and provide decent water, sanitation and electricity for all.

The biggest divergences lie in four areas, according to sources close to the negotiations.

They include action on climate change, protecting the oceans and achieving food security, and whether "Sustainable Development Goals" should replace the Millennium Development Goals when these objectives expire in 2015.

The UN has not ruled out the possibility of intense negotiations continuing right up to the leaders' summit that will be attended by French President Francois Hollande and Chinese Premier Wen Jiabao, among others.

Nations all agree that the summit comes at a turning point, and its outcome is crucial.

But privately delegates expressed doubt that a consensus on how to tackle these problems will be reached while many governments remain focused on the economic crisis.

The European Union will fight to the last for credible commitments in Rio but it will be "very, very difficult", the bloc's environment commissioner Janez Potocnik said in Brussels on Wednesday.

"After tough pre-negotiations in New York, unfortunately not enough progress has been made so we have some intense days ahead of us in Rio," the commissioner said.

Privately, EU negotiators were more forthright. "It will be very, very difficult to draw up concrete measures and fix dates," one told AFP.

"No promises were made during lead-up negotiations," said another. "There was nothing concrete, just a lot of blah-blah-blah and statements of intention."

French dreams of creating a World Environment Organisation, for instance, are not expected to see the light of day. "At best there'll be a bigger role for the United Nations Environment Programme (UNEP)," said a senior European official.

A report released ahead of the gathering described an urgent need to tackle population growth and voracious consumption that are placing Earth's resources under intolerable strain.

According to UN figures, global food demand will double by 2030 and energy consumption will soar by as much as 45 percent, putting mounting pressure on finite resources amid growing social inequality, water shortages and global warming.

Notably absent from the summit will be US President Barack Obama, who is facing a tough re-election race at home, and German Chancellor Angela Merkel.

The United States will be represented in Rio by Secretary of State Hillary Clinton.