By Beth Harris
The Associated Press

INDIANAPOLIS - The United States outtouched Australia to win the men's 800-meter freestyle relay after Michael Phelps withdrew from the World Short Course Championships because of a back injury Friday night.

Justin Mortimer overtook Australia's Joshua Krough in the final 25 meters and got his hand on the wall first. Ryan Lochte, Chad Carvin, Sycamore graduate Dan Ketchum and Mortimer were timed in 7 minutes, 3.71 seconds. Nicholas Sprenger, Andrew Mewing, Brendan Hughes and Krogh finished in 7:03.78. Brazil was third.

Phelps, an eight-time Olympic medalist, had planned to swim the relay after pulling out of the 400 individual medley preliminaries Friday morning. He won the 200 freestyle Thursday, opening night, and in the process aggravated a sore back that had bothered him for 1 1/2 weeks.

"I don't think this is a big issue," Phelps said. "I just want to be extra cautious and extra safe."

Sprenger gave Australia an early lead before Carvin put the Americans in first. With 50 meters remaining, Krogh had the Aussies back in front by two-tenths of a second before Mortimer surged past him in front of 8,782 cheering fans at Conseco Fieldhouse.

The Americans won five of eight finals Friday, giving them 10 wins in 13 events. They were 5-for-5 Thursday. But the United States' medal count is likely to be lower because of Phelps' withdrawal. He was set to swim in five individual events and some relays.

"Thank goodness it was here and not at the Olympics," Aaron Peirsol said.

Peirsol, who swept the backstroke events at the Athens Olympics, won the 100 back.

He finished in 50.72, lowering the meet record of 50.75 set by American Neil Walker in 2000.

"I didn't expect anything less," Peirsol said. "It feels good to come out on top."

Without Phelps in the 400 IM final, Oussama Mellouli of Tunisia won in 4:07.02. It was the first gold medal in an international swimming meet for the Mediterranean country. Mellouli also swims for Southern California.

Olympic silver medalist Ian Crocker won the 100 butterfly in a meet-record 50.18, and Brendan Hansen won the 100 breaststroke in 58.45.