Many say they will miss the targets unless they can buy pollution cuts from third contries, using certain trading devices which the treaty allows.

But one such tool, called Joint Implementation (JI), is struggling because of a lack of funding.

"I'm sure we'll get some money, but the question is whether it will be enough," said Janos Pasztor, an official at the UN's climate change body.

Pasztor said the present US$2 million budget shortfall could halt JI work from the week after next. The problem is that the bulk of pledges from certain countries have not been received.

Pasztor was speaking at a conference of delegates attending a 160-nation May 15-26 conference in Bonn, discussing ways to combat global warming.

JI allows Western states to buy pollution cuts from former communist East European countries and Russia and Ukraine, by investing in projects to clean up their heavy industry.

The cash problem threatens a mid-November timetable to start JI project approval, said Daniela Stoycheva, head of the UN team overseeing the JI process, a team which has three full-time staff.

Assuming the team balances its books, some 125 so-called Track 2 projects could be up and running by the end of 2007, Stoycheva said -- projects which could be worth over US$500 million at recent JI carbon prices.

A longer term difficulty facing the whole Kyoto process is its present 2012 shelf-life, when present targets and commitments end.

Talks kicked off this month in Bonn to discuss an extension but these talks could last years, given opposition both from some developing countries, which currently do not face targets, and developed countries too.

"What is quite strange to me is that developing countries are trying to create obstacles -- the country which creates this obstacle is as usual Saudi Arabia," said Stoycheva. "(But) we have a dialogue."