Delegates complained that reversals in the talks put negotiations back by a year, even before minimal gains were scored at the Copenhagen summit last December.
"It's a little bit like a broken record," said European Union negotiator Artur Runge-Metzger. "It's like a flashback," agreed Raman Mehta, of the Action Aid environment group. "The discourse is the same level" as before Copenhagen.
The sharp divide between rich and poor nations over how best to fight climate change - a clash that crippled the Copenhagen summit - remains, and bodes ill for any deal at the next climate convention in Cancun, Mexico, which begins in November.
"At this point, I am very concerned," said chief U.S. delegate Jonathan Pershing. "Unfortunately, what we have seen over and over this week is that some countries are walking back from progress made in Copenhagen, and what was agreed there."
Dessima Williams of Granada, who speaks for island states, charged that rich countries were "backsliding" on pledges of help to the poorest countries. Devastating floods in Pakistan, deadly fires and drought in Russia, a food crisis in West Africa - and reports that the first decade of this century was the hottest on record - provided a stark backdrop to the talks.
"The situation in all of our countries is worsening," Williams said.
In Bonn, negotiating text doubled in length over the last week as countries put forward claims that had been deleted last year and delegations jockeyed for last-minute advantage before heading into the final stage of negotiations before Cancun.
Christiana Figueres, the top U.N. climate official, said the Bonn meeting was the last chance for countries to put forward maximum national demands, but they must "radically narrow down their choices" at the next meeting. One more round of talks is scheduled for October in China.
Expectations for Cancun already have been deflated to avoid the sense of fiasco that followed Copenhagen, which had been invested with high hopes of a comprehensive deal and with the efforts of 120 world leaders who attended, including President Barack Obama.
Copenhagen ended with a three-page political statement pledging to limit the rise of the Earth's average temperature to 2 degrees Celsius (3.8 F) above levels recorded before industries began pumping carbon dioxide into the air 200 years ago. It promised rich nations would help developing countries slow the growth of their emissions, while reducing their own.
Figueres said the objective of Cancun was a set of operational decisions that could later be turned into an international treaty. They include the transfer of billions of dollars a year and cutting-edge energy technology from industrial to developing countries and giving them the skills to adapt to changing weather patterns, she said.
She challenged the view that the Bonn talks were a step backward. Delegates may feel let down if their issues of interest had not advanced, "but if you see the bigger picture, we have progress."
Some of the problems occurred when countries tried to translate the intentions of the Copenhagen Accord into legal documents. Runge-Metzger, the EU delegate, said China objected to U.S. suggestions on monitoring Chinese actions to contain emissions, saying they went too far in infringing on Chinese sovereignty.
Pershing declined to give details of disputes raised in closed-door negotiations, but he said major developing countries were backing away from commitments to slow the growth of their greenhouse gas emissions, and now say emission controls should apply only to industrial countries.
China, India, Brazil and South Africa were among the major developing nations at the Copenhagen summit. Since then, China has become the world's largest consumer of energy, to add to its earlier position of being the world's biggest greenhouse gas polluter.
Another point of contention, Pershing said, was an agreement in Copenhagen for wealthy countries to raise $100 billion a year by 2020 to help poor countries adapt to climate change. Now poor nations say that is not enough.
Williams, the Granada delegate, confirmed the $100 billion figure was likely to be challenged.
"It sounds very large," she said. "For the donor countries it is a lot to ask taxpayers to pay. But you must weigh that against the need" of countries that may be devastated by the effects of global warming.
Williams said one of the reasons for the setback in the talks was the recent failure of the U.S. Congress to pass a climate bill.
Some countries argued for a slowdown in the talks because the lack of legislation cast doubt on Washington's international commitment.
"That has been taken as a signal by some that nothing can occur," Williams said.
Pershing assured the negotiators, in public and in private talks, that Obama remained committed to reducing U.S. carbon emissions 17 percent from 2005 levels by 2020, and he had not given up on passing a sweeping climate and energy bill.
In the meantime, "we have multiple tools at our disposal. We will use all of those tools," he told reporters.