British songstress Lily Allen is to postpone a raft of West Coast performances after U.S. authorities revoked her work visa.

Allen was initially stopped by American customs officials when entering the country earlier this month.

Following that incident, Allen's manager Neale Easterby, of Empire Management, confirmed to Billboard that the artist had been held in customs, but was adamant her dates -- and a scheduled appearance this week at the MTV Video Music Awards -- would go ahead.

In a statement issued today on Allen's behalf, EMI said the visa reinstatement process "has proven lengthier than anticipated, thus preventing her tour from launching on Sept. 6 in San Diego, CA."

Allen added, "I am so disappointed that I won't be able to come to the States at this time," says Lily. "I was really looking forward to playing these shows and being part of the Video Music Awards. I want my fans to know that I'll be back as soon as I possibly can."

Allen's Capitol debut, "Alright, Still," has sold more than 374,000 copies in the United States, according to Nielsen SoundScan, after opening at No. 20 on The Billboard 200 in February.