DILI - Negotiators from 190 countries meeting in Bali to discuss climate change have "a political and historical responsibility" to reach a deal, UN Secretary General Ban Ki-moon said on Friday.

Asked about the consequences of not reaching a deal, Ban said "that would be very serious".

The UN Secretary General said he felt all countries, including the United States, wanted an agreement.

The United States, as well as Japan, Canada and Australia, have been disputing a guideline for rich nations to cut emissions of greenhouse gases by 25 to 40 percent below 1990 levels.

"I think there will be an agreement," he told reporters on board a flight from the Indonesian resort island of Bali, where the summit is taking place, to East Timor's capital Dili.

He warned against countries becoming fixated on emission targets.

"That will have to be negotiated down the road" he said.

Ban said he would be prepared to make an unscheduled return to Bali on Saturday if the talks were still deadlocked.

"I think the negotiators and particularly the ministers and the senior leaders have a political and historical responsibility" to conclude the talks successfully, he said.

"Climate change, global warming doesn't care where you're from," he said.