Heading to the UN Climate Conference in Cancun, officials from Venezuela say some developed countries have told them there might be no agreement on emissions targets.

Shortly after Japanese delegates proposed terminating the Kyoto Protocol, representatives from Venezuela, Bolivia, and Nicaragua said a number of unnamed industrialized nations have ruled out signing up for a new round of emissions targets, after its current phase ends in 2012.

At the start of the Cancun talks, UN officials said they want to firm up existing, non-binding emissions pledges by developed countries, but the latest news cast a shadow on the summit's possible achievements.

Emerging markets favor the Protocol, which makes a clear distinction between industrialized and developing economies, while many industrialized countries prefer an agreement which enshrines action by all major emitters.