Boris Johnson is to hold a press conference at 5pm at the climate summit Cop26 summit in Glasgow, No 10 has said.

       It comes after a series of gloomy remarks from the prime minister in recent days about the ability to thrash out an agreement at the conference to prevent global temperatures from rising more than 1.5C above pre-industrial levels.

       Ahead of the event, Mr Johnson warned fellow leaders that if the summit failed “the whole thing fails” and the landmark 2015 Paris Agreement would have “crumpled at the first reckoning”.

       However, on the second day of the summit, ministers struck a more upbeat tone, hailing a “significant breakthrough” on a deforestation agreement, with more than 100 leaders pledging to end the “great chainsaw massacre” of the world’s forests.

       Representing countries that are home to 85 per cent of the planet’s forests – including Brazil – the leaders committed to “halt and reverse” deforestation by the end of the decade at an event convened by the prime minister on Tuesday.

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       Mr Johnson told delegates: “Today is not just a vital win in the struggle to contain global temperature increases, it is also a huge economic opportunity.

       “This is the long-term sustainable path to maintaining to ending the loss of our forests, protecting our sacred biodiversity and helping to keep alive the ambition of 1.5 degrees by the end of the century.”

       Earlier, a No 10 spokesperson suggested the prime minister will also highlight other announcements at the summit so far, including commitment by almost 100 countries to cut back on the potent greenhouse gas methane.

       Nations agreed on Tuesday to slash emissions from methane by 30 per cent by 2030, when compared to levels in 2020, in what was described as a “game-changing commitment” by the US president Joe Biden.

       The prime minister’s official spokesperson also claimed: “I think we are starting to see some significant momentum over the past day and a half.”

       “The prime minister will remain closely involved in that work over the next couple of weeks,” they added.

       “This is not a foregone conclusion. What we have seen are some very early signs that we are beginning to make progress, but we are not complacent. There is a huge amount to do.”