Cop28 officials have sparked a backlash after a draft text from the Dubai summit dropped its previous commitment to "phase out" fossil fuels.
A number of nations have been left disappointed as small islands warn the new draft text is "completely insufficient".
Burning fossil fuels is regarded as a key reason driving global warming, with millions of lives at risk as a result.
The draft text replaced its commitment to "phase out" fossil fuels with a pledge to wind down the world’s dependence on coal, oil and gas.
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It also suggested ramping up renewables and switching to low carbon technologies.
Cop28 president Sultan al-Jaber, who is also chief executive of the United Arab Emirates state oil giant Adnoc, said: "The time to decide is now."
He added: “The world is watching. Let’s not rest until we get this done.
“We have made progress but we still have a lot to do."
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Members of a Spanish environmental NGO look over the "Draft text by the President" of the "First global stocktake under the Paris Agreement"
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The Alliance of Small Island States called a press conference to announce "we will not sign our death certificate".
The group also revealed: "We cannot sign onto text that does not have strong commitments on phasing out fossil fuels."
However, other nations and blocs have also come out to condemn the change to the draft text.
The US expressed a desire for the language on fossil fuels to be "substantially strengthened" and the EU's lead negotiator warned there are elements that are "fully unacceptable".
A banner hangs in a venue at the UNFCCC COP28 Climate Conference the day before its official opening on November 29, 2023 in Dubai
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Brussels even warned it would walk away from talks unless the draft text is changed.
Ireland's environment minister Eamon Ryan said: "We can’t accept the text."
He added: "It's not strong enough. It raises real problems in a whole lot of different ways."
However, a spokesperson for the presidency said: “The COP28 presidency has been clear from the beginning about our ambitions.
"This text reflects those ambitions and is a huge step forward.
"Now it is in the hands of the parties, who we trust to do what is best for humanity and the planet.”
