Pregnant pop star Lily Allen has pulled out of plans to perform at Elton John's charity ball on Saturday night due to illness.

The Smile singer was due to take to the stage at the Grey Goose Character & Cocktails Elton John Aids Foundation winter ball in London to perform for guests. Allen has now axed her appearance after falling sick with a "viral infection," and Elton has stepped up to take her place in the show.

A spokesman for Allen says, "Lily Allen is a keen supporter of the charity and Grey Goose and is sorry that she is no longer able to perform live on the night. Lily Allen regrets that she has had to pull out of her scheduled appearance due to a viral infection."

"As Lily is pregnant and not able to take medication, she has been advised to rest until the infection clears. She apologizes to Elton and to anyone attending the event."

The ball will take place at the U.S. embassy in the British capital.

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