Singapore plans to raise at least US$1.3 billion by reopening its 50-year green bond, adding to its financial firepower to combat climate change. The Monetary Authority of Singapore has tapped Citigroup, DBS Group Holdings, Oversea-Chinese Banking Corporation, Standard Chartered and United Overseas Bank to conduct the transaction, which is expected to be kicked off this week, according to a person familiar with the matter, who asked not to be identified because they’re not authorised to speak about it.