And Nastia Liukin, who will be in London to cheer on the US team, withdrew citing a lack of training after similar TV and commercial commitments.
Sandra Izbasa, the Romanian Olympic champion who would have rivalled Tweddle in the floor event, suffered a serious Achilles injury in September and was forced to withdraw.
Tweddle finished fourth behind Izbasa, Johnson and Liukin in the Beijing floor competition, leaving the 24-year-old a real chance of gold in London.
The competition concludes with both men's and women's individual apparatus finals on Saturday and Sunday, with no team or rhythmic gymnastics events to be staged.
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