LONDON -- Pop star Christina Aguilera [ tickets ] was forced to cancel her performance at the World Music Awards in Monaco on Tuesday night (5/11) and postpone a trip to the United Kingdom due to a "severe ear infection and a serious case of the flu related to exhaustion."

Her doctors advised her not to take flights over three hours and to cancel all activity for at least two weeks, according to a statement released by her label RCA.

19-year-old Aguilera also said in the statement: "I'd like to reassure my fans that my illness is not too serious, but it's important for me to rest for a while and look after my health. I am disappointed that I've had to cancel various things and I'm looking forward to getting back on my feet and visiting Europe."

As a result of her illness, the May 22 U.K. release of Aguilera's third single "I Turn to You," currently No. 21 on the Billboard Hot 100 chart, has been postponed until she is "fit enough to fly." The singer scored a No. 1 single in the U.K. last year with "Genie in a Bottle."

Aguilera was replaced at the last minute at the World Music Awards by teen rocker and "Another Dumb Blond" singer Hoku [ tickets ].