The global death toll from Covid-19 could double to two million before a successful vaccine is widely used, the World Health Organisation's (WHO) emergencies director Michael Ryan warned, as world leaders at the United Nations General Assembly called for global unity to fight the pandemic.

British Prime Minister Boris Johnson was due yesterday to pledge £340 million (S$597 million) in funding for the WHO spread across four years and call for a revival of cross-border cooperation to repair "ugly rifts".

Indian Prime Minister Narendra Modi pledged his country's vaccine production capacity would be made available globally.

Australian Prime Minister Scott Morrison insisted that any nation that develops a Covid-19 vaccine should share it universally, warning that history will be a "severe judge" if not.

Latin American leaders also appealed to the UN for free access to a future vaccine, urging major powers to share their know-how for the sake of global well-being.