People who give to the All In Challenge will be entered into a prize draw.

The campaign was launched on Tuesday to help feed vulnerable people in the US and has already raised $5.6m (£4.4m).

Ellen DeGeneres, Kevin Hart, Justin Timberlake, Justin Bieber and many US sport stars have also offered donors a chance to get up close and personal.

Bieber has promised to fly to one lucky fan's house - once the lockdown is over - for a private performance of his 2009 hit One Less Lonely Girl.

Hart has offered a speaking role in his next movie, while Timberlake and Bill Murray will give a winner a round of golf.

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 Ellen DeGeneres will let a winning donor co-host her chat show for a day

Matthew McConaughey has invited a donor to join him in his private box to watch an American Football game in Texas.

DeGeneres and wife, actress Portia de Rossi, will donate $1m (£800,000) and offer a donor the chance to co-host an episode of her chat show.

DeGeneres and McConaughey were both nominated to take part in the challenge by DiCaprio, who himself is offering a fan the chance to hang out on the set of Killers of the Flower Moon with him, De Niro and director Martin Scorsese.

"If you ever wondered what it was like to be able to work with the great Martin Scorsese, this is your chance," DiCaprio said.

Killers of the Flower Moon tells the story of Native American killings in 1920s Oklahoma.

DiCaprio also recently launched America's Food Fund, to which he and Laurene Powell Jobs - widow of Apple co-founder Steve Jobs - gave a combined $5m (£4m).

The organisers of the All In Challenge hope to raise $100m (£80m) for children, the elderly and frontline workers, via such charities as Meals on Wheels, No Kid Hungry and America's Food Fund.

As the coronavirus pandemic has gone on, however, there has also been a backlash against the celebrity world.

While many high-profile names have dug deep, there have been calls for more stars to give generously themselves, while a string of celebrities have been criticised for posting self-indulgent videos.

They include Madonna talking about how Covid-19 is "the great equaliser" while sitting naked in a milky bath full of rose petals; Gal Gadot leading an all-star cover version of Imagine; and Sam Smith having a "quarantine meltdown".

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That all led Ricky Gervais to say recently: "I see someone complaining about being in a mansion with a swimming pool. And, you know, honestly, I just don't want to hear it."

Other stars who have helped coronavirus causes include:

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Lady Gaga and Rihanna have contributed to the coronavirus cause

• Lady Gaga has worked with the Global Citizen movement to raise $35m (£28m) through corporate and philanthropic donations, and is organising the all-star Together At Home concert this weekend.
• Rihanna's Clara Lionel Foundation has donated $5m (£4m) for causes like food banks, testing in Africa, and protective equipment, and has separately said she has given $2.1m (£1.7m) to help domestic violence victims in LA.
• Sir Elton John donated $1m to help "respond to the effects of COVID-19 on HIV care for the most marginalised communities around the world", and hosted the iHeart Living Room Concert For America, which raised $10m (£7.9m).
• U2 have donated €10 million (£8.6m) to buy personal protective equipment (PPE) for frontline staff in Ireland, with Bono personally lobbying businesspeople to secure supplies (as well as offering a song inspired by the crisis).
• Oprah Winfrey has said she is giving a total of $10m (£8.01m) "to help Americans during this pandemic in cities across the country and in areas where I grew up".
• Actors Damian Lewis, Helen McCrory and Matt Lucas have raised £1.1m through a campaign to feed NHS workers.