A 30-billion-dollar pledge for the period 2010-2012 to help poor countries green their economies and cope with climate change impacts was one of the few concrete measures to emerge from last year's nearly-failed summit.

But six months later there is little sign of the money.

"We need real implementation of the funding, real action on the ground," said Dessima Williams, chief negotiator of Grenada, representing the Association of Small Island States (AOSIS).

"There is absolute and continued urgency."

Nor are there any clues as to how financing will be ramped up to at least 100 billion dollars annually by 2020, another provision mandated by the Copenhagen Accord.

Ideas floated include a micro-tax on financial transactions, a carbon trading scheme for the aviation and shipping sectors, and "green bonds" issued against rich-country funds held by the International Monetary Fund (IMF).

But so far none of these politically risky schemes have much traction.

"If the sense is that this is all a sham and countries are not following through on their commitments, it will really undermine the trust you need to get something done," said Alden Myer, a policy analyst at the Washington-based Union of Concerned Scientists.

Financing is only one of several thorny issues on the table as the 12-day talks under the 194-nation UN Framework Convention on Climate Change (UNFCCC) get under way.

Negotiators must also work towards upholding the Accord's other core provision of preventing global temperatures from rising by more than 2.0 degrees Celsius (3.6 degrees Fahrenheit).

Voluntary pledges from industrialised nations and emerging giants such as China -- even if met -- would yield an increase of 3.0 C to 4.0 C, putting the planet on a trajectory for catastrophe, say scientists.

There are also complex wrangles over technology transfer, how to monitor and verify national plans to cut greenhouse gases, and the mechanisms for disbursing aide.

But the UN talks remain bogged down by procedure, unable even to decide on whether or how to incorporate the Copenhagen deal -- cobbled together by a handful of nations at the 11th-hour -- into the formal UN process.

At the same time, political ambition has been dampened by the fallout from crushed expectations in the Danish capital, and concerns about the fragile state of the world economy.

"The mood is one of realism and accepting incremental changes rather than one 'Big Bang' agreement," said Saleemul Huq, senior researcher at the International Institute for Environment and Development (IIED) in London.

Outgoing UNFCCC Executive Secretary Yvo de Boer told journalists that the chances of forging a legally-binding climate treaty -- the avowed aim of all parties -- before year's end are now vanishingly small.

Since January, many nations have opted for a "building block" approach, laying the bricks of a future climate deal outside the UN framework in smaller, multilateral meetings focusing on a single region or sector.

An initiative, for example, spearheaded by France and Norway produced an agreement last week to boost funds to protect forests to four billion dollars up to 2012.

Deforestation accounts for about 17 percent of global greenhouse gas emissions.

"We want to demonstrate that it's possible to start coordinated action [on forests] while we have formal negotiations under way at the UNFCCC. The world needs to see this," Brazilian Environment Minister Izabella Teixeira told journalists days before the deal was sealed.

But some negotiators worry about losing sight of the big picture.

"We have to be very careful that the piecemeal approach does not mean that the large overarching framework is not achieved, so that we wind up with a gap," Williams said.

Over the next week, talks will focus on a 42-page text unveiled in the run up to Bonn and intended as a rough draft of a future agreement.

Informal comments from negotiators show how hard it is going to be to bridge the gap, said Meyer.

Bolivia and several other developing nations "say it reflects much too much of the Copenhagen Accord, while the United States is complaining that there is almost nothing in it from the Accord," he said.