Music
The 'Smile' singer was due to kick off the tour in San Diego on September 6 but her spokesman said the process of reinstating her papers had "proven lengthier than anticipated".
US authorities cancelled Allen's visa earlier this month after she was questioned at Los Angeles Airport over a clash with a photographer in London.
The 22-year-old said: "I'm so disappointed. I want my fans to know that I'll be back as soon as I possibly can."
It was earlier revealed that Allen has been dropped from the line-up for the MTV Music Awards in Las Vegas, where she is nominated as best newcomer.
But her record company denied the reports, saying: "She was not dropped from the awards and MTV are hugely disappointed that she will not be able to participate."
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