Stacy Dragila notched up her sixth successive pole vault victory on the first day of the United States Indoor Track and Field Championships in Atlanta.

The Olympic champion struggled to find her form failing to clear 15 feet (4.5m) for the first time in more than a month.

"It's nice to know that I'm human and I still have things to work on," said 29-year-old Dragila.

Dragila finished just ahead of Sydney finalist Kellie Suttle, who improved on her personal best by a centimetre.

Dragila and Suttle will represent the U.S. at the World Indoor Championships next weekend in Lisbon, Portugal.

In the 200m, Kevin Little, the 1997 World champion, posted the fastest time finishing his heat in 20.61 secs.

James Davis cruised to a personal best in the 400m, recording a time of 45.79 secs to make him the third fastest man in this winter season.

Tiombe Hurd recorded 14.04m to win the triple jump but failed to qualify for Lisbon.

The event concludes on Saturday.