LONDON » The U.S. women are atop the Olympic gymnastics standings, as expected, with little standing in their way — except themselves.

More than the Russians, Romanians and Chinese, the biggest challenge for the gold medal may come from how they deal with world champion Jordyn Wieber’s failure to qualify for the all-around final Sunday. She was bumped by her best friend on the very last routine.

"I’m definitely worried," national team coordinator Martha Karolyi said. "You try to find words … what do you say? But the fact is the fact. She did her best. She was edged by her teammates."

A heavy favorite for gymnastics’ biggest prize — and the attention and riches that go with it — Wieber lost her chance with a series of uncharacteristic mistakes. She wound up with the fourth-best individual score in qualifying, but countries are limited to two gymnasts in the all-around and event finals and pal Aly Raisman and Gabby Douglas were ahead of her.

Russia’s Viktoria Komova, who was runner-up to Wieber at last year’s world championships, is ahead of all three Americans.

The 17-year-old Wieber was sobbing as she made her way through the mixed zone, so distraught she couldn’t speak to reporters. Later on Twitter, she thanked fans for "all your love and support."

"I am so proud of our team today and I can’t wait for team finals!!" she wrote.

It could be a historic competition for the Americans, who breezed to the top of qualifying with a score of 181.863 points and then waited to see if Russia, Romania or defending Olympic champion China could match it.

No one came close. Russia, runner-up to the U.S. at last year’s world championships, was 1.4 points back (180.429), while China (176.637) and European champion Romania (176.264) were well behind.

"We knew the Americans were going to be up there," said Rebecca Tunney of Britain, which was in the same qualifying session as the Americans. "They’re going to be unbeatable."

Scoring starts from scratch in Tuesday’s team finals. The Americans are the strongest team top to bottom — if they can get their heads around Wieber’s woes.

After congratulating Raisman, Wieber rushed off to try to compose herself — unsuccessfully. Her teammates were similarly shell-shocked, with Raisman looking particularly stunned.

"I was really surprised, and I feel awful because she wanted it so bad," Raisman said. "But she should still feel proud because she’s an Olympian. We have to stay calm and focused on team finals."