Members of the Sierra Club in Cancún make their feelings clear about countries they say avoid the issue of climate change. Photograph: Ronaldo Schemidt/AFP/Getty Images

The UN climate talks in Cancún were in danger of collapse last night after many Latin American countries said that they would leave if a crucial negotiating document, due to be released tomorrow, did not continue to commit rich countries to emissions cuts under the Kyoto protocol.

The Bolivarian Alliance for the Americas (Alba) group of nine Latin American countries – who claim they are backed by African, Arab countries and other developing nations – said they were not prepared to see an end to the treaty that legally requires all of its signatories to reduce greenhouse gas emissions.

They challenged the Mexican presidency of thewhere one country, presumably Australia, had said "they might as well go to the beach" rather than set new pledges for Kyoto. "We will not accept the destruction of the Kyoto protocol in exchange for anything. The new text must include the second period of Kyoto," she said.

Wealthy countries were last night trying to avoid a diplomatic disaster, saying they were not trying to kill Kyoto. Britain and the EU have said they are prepared to sign up to a second commitment period – provided others do so too.

Developed countries have indicated in closed meetings that there is now little chance of a second commitment period for Kyoto being negotiated in Cancún.

Few heads of state are expected to attend this year's talks – in sharp contrast to the