Americans Graham Rahal and Townsend Bell led 22 qualifiers in filling the Indianapolis 500 grid on Saturday in the penultimate time trial session for the 25 May race.

Venezuela's Milka Duno and American Sarah Fisher joined US driver Danica Patrick to give the Indy-car classic three women behind the wheel, while 12 non-US racers boosted the global contingent in the 33-car event to 20 drivers.

New Zealand's Scott Dixon captured pole position in last Saturday's first day of qualifying, when the front 11 spots in the field were filled.

Bell qualified for the 12th spot, the outside of the fourth row, at 222.539mph with 19-year-old Rahal, who last month became the youngest race winner in Indy-car history, just back at 222.531mph on the inside of row five.

Only .006 of a second came between the racers over a four-lap qualifying run at the famed 2.5-mile (4km) Indianapolis Motor Speedway oval.

"I didn't realize how close that was," Bell said. "We got four consistent laps. I really wanted to focus on making those four laps work. It was tough. Conditions were tricky."

Canada's Marty Roth was the slowest and last qualifier, filling the field at 215.506mph but making himself the man on the "bubble", the target speed for unqualified rivals in Sunday's final qualifying session.

"It's a disappointing day," Roth said. "We got the car working. We were running early in the morning 222s. To qualify where we did, it's disappointing. It makes for a long day tomorrow."

American A.J. Foyt, Italy's Max Papis and Mexico's Mario Dominguez are the drivers expected to challenge Roth for the final spot. Dominguez and Papis were involved in crashes Saturday but neither was seriously injured.

US racer Phil Giebler suffered bruised lungs in a practice crash and was hospitalized overnight, his only car shattered to end his qualifying hopes.

Americans Buddy Lazier and Roger Yasukawa were second and third on the bump list and preparing for a tense Sunday.

"It's definitely nerve wracking," Yasukawa said.

England's Darren Manning and Brazil's Bruno Junqueira joined Rahal in row five.

England's Justin Wilson and Americans Buddy Rice and Davey Hamilton were on row six and England's Alex Lloyd was in row seven with Americans Ryan Hunter-Reay and John Andretti.

Fisher was in row eight with Australian Will Power and American Jeff Simmons with Spain's Oriol Servia joined by Duno and her compatriot, E.J. Viso in row nine.

An all-Brazilian 10th row featured Mario Moraes, Enrique Bernoldi and Jaime Camara.