NEW YORK • The Rocket Man has been brought down to earth.

Last Saturday, Elton John posted that he had to cancel a concert that evening in Indianapolis in the United States because he was "extremely unwell".

"It is with the heaviest heart that I'm forced to deliver the news that I am extremely unwell and therefore unable to perform. I absolutely hate to let my fans down, but I owe it to you to put on the best show possible and, unfortunately, that's simply not possible," he wrote.

He promised to "deliver the show you deserve" in the city when he returns in March next year.

While John, 72, did not say why he was feeling down and out, a report in trade publication Variety noted that his mother-in-law died last Thursday.

His husband is film-maker David Furnish, 57, who, in his online tribute to his mother, wrote: "You lived your life impeccably. I will never forget you.

"I promise to do my best to pass the gifts you gave to me on to my own beautiful sons."

Furnish and John are parents to two sons.

In a show in Toronto in Canada last Thursday, John dedicated his 1974 chart hit Don't Let The Sun Go Down On Me to her.

There is no word if a show, scheduled for today in Nashville as part of his farewell tour, will proceed.