United States President Joe Biden has opened a Covid-19 summit of world leaders with a promise to donate a “historic” extra 500 million vaccines to countries struggling to push back against the pandemic.

“This is an all-hands-on-deck crisis,” Biden said. The pledge from Biden at the summit, held virtually from the White House, brings the total US commitment of donated vaccines to 1.1 billion — more than the rest of the world combined, according to an AFP report.

“The US has already shipped 160m of these doses to 100 countries,” the White House said in a statement. “For every one shot we've put in an American arm to date, we are now donating three shots globally.”