The Parker gymnast took herself out of the mix for the U.S. team on Monday, saying she needs more time to get in shape.
Liukin has spent much of the past year on the road, and returned to competition only in late July.
She did one event at the national championships two weeks ago, finishing fourth on balance beam.
“I have given a lot of thought to this since the 2009 Visa Championships,” said Liukin, who competed in the Visa Championships in Dallas earlier this month. “Getting back into the gym and competition has been a major goal for me this summer, and I have worked hard to balance my training and obligations. This past year has been wonderful and a whirlwind. With the selection process for Worlds beginning next week, I realized I need to take some time to get myself where I need and want to be competitively. Competing at a World Championships is an incredible experience, and I look forward to supporting my teammates as they prepare for London. "