The United States and China have released a rare joint declaration on climate change, saying "there is more agreement between China and the US than divergence”.
The world's biggest polluters have committed to "enhanced climate actions that raise ambition" in the "critical decade of the 2020s".
US climate envoy John Kerry told reporters at the COP26 climate conference in Glasgow that there was not just an effort but an "imperative to co-operate".
Speaking through an interpreter, China's top negotiator Xie Zhenhua said there was "more agreement between China and the US than divergence".
The joint statement, agreed just hours earlier, promises decisive action in the "critical decade of the 2020s".
It sets out plans to work together on tackling the potent gas methane - a key way of cutting short-term warming - and agrees on the need to step up on stopping deforestation.
China also commits to "phase down coal consumption" during the 15th Five Year Plan [which covers 2026-2030] and make best efforts to accelerate this work.
Bernice Lee, from the Chatham House think tank, said though some detail is patchy, the statement should "dissolve any fears that US-China tensions will stand in the way of success at COP26.
"But the statement is not enough to close the deal. The real test of Washington and Beijing is how hard they push for a 1.5C aligned deal here in Glasgow," she said.
Boris Johnson returned to Glasgow on Wednesday in an attempt to propel the talks forward in their final few days.
He accused countries of "patting themselves on the back" in the six years after signing the Paris Agreement, but "quietly edging toward default, now that vulnerable nations and future generations are demanding payment here now in Glasgow."
There is an expectation on the UK as COP26 host to get a good outcome and the first draft of an agreement was published on Wednesday morning.
It "calls upon" parties to "accelerate the phasing-out of coal and subsidies for fossil fuels".
Such a phrase has never appeared in a final UN climate text so its likely to be highly contested, for example by fossil fuel exporters like Saudi Arabia or those still highly dependent on coal.
Another bone of contention could be the section urging nations to revisit and strengthen their 2030 carbon emissions targets by the end of 2022.
Meeting the Paris Agreement target of limiting warming to "well below" 2C and ideally 1.5C above pre-industrial levels requires "meaningful and effective" action in "this critical decade", the draft text says.
Pearnel Charles Jr is Jamaica's climate change minister, leading the country's negotiations at COP26.
"At 1.5C, Jamaica loses beaches, coral reef dies and employment plummets. Crime goes up," he told Sky News.
For his island nation, getting an ambitious deal in Glasgow is the difference between someone's "daughter going to school" or even being able to feed her because their work in fishing has "vanished".
Scientists warn that keeping temperature rises to 1.5C, beyond which climate change will hit even harder, requires slashing global emissions by 45% by 2030.
But the planet is already around 1.1C hotter and on Tuesday an independent assessment found current plans set us on a path of 2.4C of warming.
A tense back and forth between negotiators, ministers and leaders will ensue as almost 200 countries desperately seek to strike a final deal by the end of the week. A "near final" version is expected to be published overnight.
While the commitment to 1.5C has been welcomed by some, others have criticised a lack of progress on loss and damage, which refers to the damages from climate change to things like homes, jobs, coastlines and lives.
Tasneem Essop, chief of Climate Action Network, told Sky News: "We echo the calls from small island states and other developing countries that the time to deliver funding for loss and damage is now. This is a matter of climate justice and human rights."
On the thorny issue of climate finance, the text urges funding for developing nations to go "beyond USD 100 billion per year", a target set for 2020 but likely not to be met until 2023.
It also pressures developed countries to give "greater clarity" on how they are going to meet their funding promises.
Who and how the world pays for developing nations - who often have contributed little to climate change but are highly vulnerable to it - to cope with a hotter world has been a sticking point in previous COP summits.
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