NEW DELHI, Nov 1 (Reuters) - British Prime Minister Boris Johnson is set to announce a sovereign guarantee for a $1 billion World Bank loan for India to develop green infrastructure, three sources familiar with the matter told Reuters on Monday. The announcement is likely to be made during the United Nations COP26 summit in Glasgow, Scotland, which has been billed as a make-or-break here chance to save the planet from the most calamitous effects of climate change. “The UK’s biggest finance offer to India at COP26 will be a $1 billion sovereign guarantee for additional World Bank lending for green infra,” said one of the sources. They declined to the named as they were not authorised to talk to the media on the subject. Spokespeople for the Indian and UK governments did not immediately respond to requests for comment. Delayed by a year because of the COVID-19 pandemic, COP26 aims to keep alive a target of capping global warming at 1.5 degrees Celsius (2.7 Fahrenheit) above pre-industrial levels - the limit scientists say would avoid its most destructive consequences. Wealthy nations face mounting pressure to deliver on an unmet pledge, made in 2009, to spend $100 billion a year to help finance an adequate response by developing countries to rising global temperatures. India"s chief economic adviser has urged rich nations to commit much more than $100 billion here to help poor countries fight climate change because of their high historical share of emissions. Asia’s third largest economy plans to keep adding renewables to its energy mix and push industries to see the benefit of using cleaner fuels, but has stopped short of committing to a net-zero emission target year. Writing by Sudarshan Varadhan; editing by Barbara Lewis