The UK taxpayer is to stop funding fossil fuel projects overseas as part of the government’s push for international action on the climate ahead of a key summit on Saturday. Taxpayers helped to support more than £21bn of fossil fuel development overseas in the last four years, despite calls from green campaigners to halt the finance. Boris Johnson said: “Climate change is one of the great global challenges of our age, and it is already costing lives and livelihoods the world over. Our actions as leaders must not be driven by timidity or caution but by ambition on a truly grand scale.” The halt to funding for fossil fuels has been mooted since early this year, when the prime minister was stung by accusations of hypocrisy because the UK continued to fund such developments despite preparing to host the next round of vital UN climate talks, Cop26, in Glasgow. The Cop26 conference has been postponed until next November because of coronavirus, but on Saturday Johnson will co-host – alongside the UN secretary general, António Guterres, and the French president, Emmanuel Macron – an interim summit of world leaders at which all countries are expected to come forward with strengthened targets to cut emissions by 2030. The UK has already set a fresh target of cutting emissions by 68% by 2030, and on Friday morning EU member states announced that they had agreed to strengthen their target for cutting greenhouse gas emissions in the next decade, in line with their long-term goal of net-zero carbon by 2050. The EU has committed to cut carbon by 55% by 2030 compared with 1990 levels, after member states wrangled into early Friday morning as Poland held out for concessions. “Today’s agreement puts us on a clear path to climate neutrality in 2050,” said Ursula von der Leyen, president of the European commission. While member states rejected the stiffer carbon cuts of 60% that the EU parliament had called for, the plan puts the EU ahead of most of the world’s major economies on tackling the climate crisis. Campaigners said the EU could have gone further. Sebastian Mang, Greenpeace’s EU policy adviser, said: “Governments will no doubt call it historic, but the evidence shows this deal is only a small improvement on the emissions cuts the EU is already expected to achieve. It shows that political convenience takes precedence over climate science, and that most politicians are still afraid to take on big polluters.” On Saturday, five years after the adoption of the Paris climate agreement, more than 70 world leaders will gather online for the Climate Ambition summit to set out fresh commitments on the climate crisis. Current commitments under the Paris agreement are insufficient to meet its goal of keeping global temperature rises well below 2C more than pre-industrial levels, which scientists regard as the outer limit of safety, with an aspiration to hold rises to no more than 1.5C. Under the accord, nations must increase their targets every five years in line with the long-term goal, which means submitting new national plans – called nationally determined contributions (NDCs) – for the carbon cuts they will make between now and 2030. Many are likely to miss this year’s deadline of 31 December for new NDCs because of the coronavirus pandemic, but the UN, UK and France, as co-hosts of the summit, are hoping all of the 70-plus countries represented will submit fresh targets. Guterres told the Guardian in an interview that new commitments were urgently needed: “We know that we are not yet where we should be. We know that five years after the Paris agreement, climate change is still running faster than we are,” said the UN secretary general. “I see this summit as a very important moment of pushing for the right momentum to grow.” Many big economies have come forward with long-term goals to reach net-zero emissions around the middle of the century. China will reach carbon neutrality by 2060, while the EU, Japan, South Korea, the UK and a host of smaller economies will do the same by 2050. The US president-elect, Joe Biden, has signalled his commitment to reach net zero by 2050, though he will play no official part in Saturday’s summit and Donald Trump’s administration has shunned the meeting. These commitments, if carried through, place countries responsible for about two-thirds of global carbon emissions under a net-zero target. According to an analysis by Climate Action Tracker, that would put the world on track to heating of 2.1C, within striking distance of the Paris goal. The race is on to sign up the remaining countries, but some will be hard to persuade. Guterres mentioned India, Indonesia, Russia, Australia and Brazil as countries that it was “important to have on board”. Brazil set out a plan earlier this week to reach net-zero emissions by 2060, but it was largely derided as containing little concrete detail and failing to address the need to stop deforestation. Laurence Tubiana, the chief executive of the European Climate Foundation and, as a French diplomat, a key architect of the Paris agreement, called the pledge “very disappointing” and “lacking credibility”. The effort was not enough to gain Brazil a coveted speaking slot at the summit, which are open only to countries with strong new plans. Australia has also been denied a slot after its prime minister, Scott Morrison, claimed he would speak. Russia and Indonesia will likewise be absent, but India, another major emitter that is highly dependent on coal, will speak at the summit, and there are hopes the prime minister, Narendra Modi, will make a fresh commitment. Guterres said: “India is making an enormous effort. But India has huge challenges in development. So it’s very important to create the mechanisms that make India understand that international solidarity is there … to allow India to be part of the net-zero coalition, as we believe is essential, recognising that they are already making a huge effort.” The summit is a staging post for the next formal UN meeting under the Paris agreement, Cop26. Gaining commitments from the missing countries, and more detailed plans from some governments that have signed pledges but have few policies in place to meet them, is now the key goal for the UN and the UK, as hosts of Cop26. Laurent Fabius, who as French foreign minister oversaw the Paris agreement, told the Guardian: “There has been some sort of revolution in climate change, internationally, with statements from China, South Korea, Europe and Biden. The great difficulty now is to implement the Paris agreement. Now is the time for action, and the Climate Ambition summit is a moment of opportunity.”