Lionel Richie said that King Charles is "doing fantastic" as the monarch steps back into royal duties.
While attending the inaugural King's Trust Global Gala in New York, the American singer spoke about the King's health following his cancer diagnosis.
Richie, who serves as a King's Trust Global Ambassador and Chairman of the Global Ambassadors Group said: "Happily I can say, he is doing fantastic."
Several famous faces including Drew Barrymore, Dominic West and Kate Moss attended the event that took place at Casa Cipriani in New York.
Richie told People Magazine: "Again, I understand, he needs to sit still, you know what I’m saying.
"The most important part is he is doing well. He’s back to his duties and so therefore, I wouldn’t want the first thing for him to do is come over — let’s not prove anything here.
“We are here to represent and we’re gonna do a great job of that.”
The American Idol star went on to explain that he was expecting a phone call from the King to find out how the evening went.
Richie said: "Believe me, my question [from him] now is, ‘How was it?’ After I finish tonight, I’m gonna get that call saying, ‘Well, how was it?’"
A message from the King was also read out during the event by Ariana, a young beneficiary of the trust.
The letter read: "Ladies and Gentlemen, it gives me enormous pride and pleasure to be able to celebrate this evening, the first ever King’s Trust event.
"When I started the Trust in 1976, I could never have imagined the reach that the organisation would have in the UK and in more than 20 countries around the world, or the more than a million brilliant young people we have been able to support."
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The King has slowly returned to his duties as he continues to receive cancer treatment on the recommendation of his medical team.
Earlier this week, the King and Camilla were presented with their first-ever vegan Coronation roll.
The couple were shown the "extraordinary" 21-metre roll at Buckingham Palace which had not been printed on calfskin because of animal welfare concerns.
The scroll contains information about the planning of the Coronation and a description of the ceremony.