US resists setting target on cutting carbon pollution

· Call to reduce emissions by 25-40% is key issue
· Democrats would back limits, says Kerry

The environment secretary, Hilary Benn, will today begin attempts to persuade the US administration to agree firm targets on carbon pollution as part of a new deal on global warming. Benn arrived at UN climate talks in Bali last night, as the US said it was unwilling to approve a draft agreement which called on developed countries to reduce emissions by between 25% and 40% by 2020.

The US said the proposal, which is backed by Britain and the EU, was "totally unrealistic" and "unhelpful". Other countries, including Japan and Canada, are also believed to be against the idea.

The US said it was in Bali to be "constructive" and wanted the meeting to agree a roadmap to a new agreement on climate change which would be concluded by 2009. But it said it would not agree a firm target, presented either as an emissions reduction or as a maximum temperature rise. European negotiators argue that a target is needed to reflect the urgency of the problem and to encourage industry to invest in green technology. The high-level segment of the talks begins tomorrow, when senior ministers replace civil servants at the negotiating table.

In an unusual step, the UN published the text of the four-page draft agreement, based on the first week of informal discussions, on its website over the weekend. It is now being argued over by the 190 countries present. Observers said the draft would be repeatedly modified and updated through the week, until a final version is agreed on Friday.

The initial draft agreement calls for a response to the "unequivocal scientific evidence that preventing the worst effects of climate change will require [developed countries] to reduce emissions in a range of 25-40% below 1990 levels by 2020 and that global emissions of greenhouse gases need to peak in the next 10 to 15 years".

The senior climate negotiator for the US, Harlan Watson, said: "We have problems with defining the numbers up front. In our view, that pre-judges the outcome of the negotiations over the next two years." He said the US supported the concept of a "shared global goal" to address climate change, but did not want the Bali meeting to discuss exact numbers.

The 25-40% figure is based on the work of the UN's Intergovernmental Panel on Climate Change, which was formally awarded the Nobel peace prize jointly with Al Gore yesterday. Watson said the IPCC calculation was based on "many uncertainties". The head of the UN climate secretariat, Yvo de Boer, said the 25-40% figure would be a "critical issue" at the talks, an important signpost in the fight against global warming. British officials said they expected the US to object to the proposal, but that the Bush administration had engaged in the talks more than in previous years. However, leaked papers revealed that US opposition to the 25-40% figure may be having an effect, with the target removed from a separate document on the future commitments of countries that have ratified the Kyoto protocol.

John Kerry, the US senator and losing presidential candidate in 2004, told the Bali event that a Democratic successor to George Bush in 2009 would bring the US fully on board. "Every single Democratic candidate for president has embraced mandatory caps ... and expressed their willingness to immediately be part of the Kyoto discussions and try to find a successor agreement to Kyoto," he said.

China has already said it may wait for 2010 before signing up to a new deal, to see how the new US president responds.

Bali negotiations

The Bali talks are aimed at agreeing a way to develop a new global treaty to replace the Kyoto protocol when it expires in 2012. That goal is made more complicated because some countries, including the US, have refused to join Kyoto. So there is a twin-track approach.

The simplest way would probably be for Kyoto members to agree new targets and timetables, which in time would draw in large developing countries such as China and India - the Kyoto track. But that would exclude the US, the largest polluter of all. So there are parallel negotiations on a broader new treaty to include them - the Bali roadmap track.

However it is achieved, a new treaty needs to be agreed by 2009-10, in time for it to come into force in 2013.