Delegates at a conference in Berlin seeking to save the troubled Kyoto Protocol say a conclusive deal looks increasingly unlikely, with new talks probably needed in the autumn to resolve differences.
Conference officials said they would present a broad compromise package to overcome squabbling over fine print that has bogged down proceedings. European Union officials also hoped a parallel conference of leaders from G8 industrial nations in Genoa would give compromise efforts a boost.
With the ten-year-old negotiations in disarray because of the US pullout from the treaty, nations are seeking to flesh out a compromise but are finding they are divided even with Washington out of the picture.
On the third of four days of ministerial level talks, officials are increasingly looking to the next scheduled United Nations meeting on climate change, due to start in the Moroccan city of Marrakesh in late October.
"We are looking at the possibility of progress in a number of areas," said Mr Baghir Asadi, chief Iranian delegate and chairman of the G77 group of developing nations. "The process will definitely continue in Marrekesh."
"It would be quite difficult (to reach a deal here) given the outstanding issues," he told reporters.
Today's talks follow a week at which more than 180 countries have been trying to finalise rules on how to implement the 1997 UN pact on cutting greenhouse gas emissions. The ministerial-level talks are due to end tomorrow night.
The Kyoto Protocol requires developed countries to cut their greenhouse gas emissions by an average of 5.2 percent by 2012.
The United States, which signed the deal under President Bill Clinton, pulled out in March with President George W. Bush saying it was "fatally flawed" and would damage the economy.
The other countries have decided to plough ahead - with varying levels of enthusiasm for keeping a treaty that will exclude the world's biggest polluter.