Paris: From Billie Eilish in New York to BTS in Seoul and Elton John in Paris, one of the biggest-ever international charity events was set to kick off Saturday with concerts around the world to raise awareness on climate change, vaccine equality and famine.

Concerts are being broadcast globally from London, Lagos, Rio, Sydney, Mumbai and more, scheduled to coincide with the UN General Assembly this week.

Eilish, Coldplay and Jennifer Lopez will perform in New York´s Central Park, where Britain´s Prince Harry and Meghan Markle will also be on stage.

Stevie Wonder will play in Los Angeles, while Ed Sheeran will headline in Paris alongside Elton John, Black Eyed Peas and Stormzy.

Tens of thousands of spectators are due to attend the biggest concerts, on condition of vaccination proof or negative Covid tests.

There will also be pre-recorded performances from BTS in South Korea, Green Day in Los Angeles, DJ superstar Alok in Rio, Kylie Minogue in London and Andrea Bocelli in Tuscany.

A slew of other artists -- including Metallica and The Weeknd -- are also involved, either through live or filmed performances.

Global Citizen said it wants one billion trees planted, one billion vaccines delivered to the poorest countries and meals for 41 million people on the brink of famine.

Tickets to Saturday´s shows were distributed free of charge to randomly selected people who signed up for the app and shared its petitions and messages on social media.

The head of the World Health Organization, Tedros Ghebreyesus, lent his support to the latest campaign, urging vaccine equality.

"We now face a two-track pandemic of haves and have-nots," he said.

"We cannot disregard this gross inequity or become complacent."

One performer who almost had to cancel was Elton John, who this month announcing he was delaying the rest of his touring dates for this year following a hip injury.

But he said he would wait until after the Global Citizen Live gig for his operation "as I don´t want to let a charity down".