MELBOURNE, Australia (AP) – Michael Phelps set another world record in the pool Friday night. This time, he needed help from his American teammates, including Ryan Lochte, who outdid Mr. Phelps with two world records at the world championships.

Overshadowed by bigger names on the American men’s team and a frequent runner-up, Mr. Lochte emerged in his own right with a stunning victory in the 200-meter backstroke, snapping teammate Aaron Peirsol’s seven-year winning streak.

“I just dug deep and went for it,” Mr. Lochte said. “He’s a great competitor, but you can’t always win every race, every day.”

Tell that to Mr. Phelps.

Mr. Lochte came back later and joined Mr. Phelps, Klete Keller and Peter Vanderkaay for a world-record victory in the 800 freestyle relay, making Mr. Phelps 5-for-5 this week with four world records in as many days.

The quartet touched first in 7 minutes, 03.24 seconds, lowering the time of 7:04.66 set by Australia at the 2001 world championships in Fukuoka, Japan.

It was Mr. Lochte’s second world record of the night to go with his new standard in the 200 backstroke.

And he earned his first gold medal in Melbourne, having been runner-up to

Mr. Peirsol in the 100 back and Mr. Phelps in the 200 individual medley.

“Some people go out there and swim for second because they don’t think they can beat a Phelps or a Peirsol,” he said. “I go in there and honestly think I can.”

Mr. Phelps swam the leadoff relay leg, getting the Americans under world-record pace on the first of his four laps. For once, though, he couldn’t quite manage a world record. His 200 split of 1:45.36 was much slower than the world record of 1:43.86 he set in winning the 200 free Tuesday.

“It was a little bit slower than what I wanted,” Mr. Phelps said.

Australia took the silver and Canada earned the bronze.

As Mr. Vanderkaay plowed home far ahead of the developing race behind him, Mr. Phelps shouted, “Come on, Peter!” Vanderkaay hit the wall and climbed on the deck for a group embrace. Phelps pumped his left arm as the scoreboard flashed `World Record’ for seemingly the umpteenth time this week.

“I’m definitely very pleased with another world record,” he said. “I’m tired and sore, but I’m still feeling decent in the water.”

America owns a leading 23 medals through six days, including 13 golds. Australia has 15 medals and six golds. Friday’s records made it 12 during the meet – with 10 set by the Americans.

In the backstroke, Mr. Lochte notched a world record and a gold medal over Mr. Peirsol, the world’s dominant backstroker who hadn’t lost a 200 internationally since the 2000 Sydney Olympics.

“I still don’t think it’s true,” Mr. Lochte said. “I think what that scoreboard says is a lie. I’m in shock.”

Before Mr. Phelps joined the relay, he and American rival Ian Crocker faced off in the same semifinal of the 100 butterfly. Mr. Crocker, the world-record holder, led all the way and qualified fastest in 51.41 seconds.

Mr. Phelps was fifth at the turn and came home third at 51.92. His time was fourth-quickest – behind Mr. Crocker, Albert Subirats of Venezuela and Lyndon Ferns of South Africa – heading into Saturday night’s final.

Mr. Crocker is the two-time defending world champion and only man ever to break the 51-second barrier, but Mr. Phelps beat him for Olympic gold in Athens.

Until Friday, Mr. Lochte was best known at this meet as the goofball who flashed a gold, silver and diamond-crusted grill in his mouth on the victory stand after the 200 IM. His teammates had dared him to wear the shiny metal caps favored by rappers.

But he was all business against Mr. Peirsol, the world and Olympic champion.

Mr. Peirsol was under his own world-record pace through 150 meters. He and Mr. Lochte went stroke-for-stroke over the last 50 meters.

“I kind of looked up at the scoreboard to see where I was,” Mr. Lochte said. “I probably shouldn’t have done that, but I saw I was right there with him. I just moved my arms faster and kicked. It’s amazing.”

Mr. Lochte touched the wall in 1 minute, 54.32 seconds.

That erased Mr. Peirsol’s old mark of 1:54.44 set at last year’s Pan Pacific championships. Mr. Peirsol finished in 1:54.80.

Mr. Lochte leaped in the water, a huge grin spreading across his face before he and Mr. Peirsol embraced across the lane ropes.

“He definitely earned it,” Mr. Peirsol said. “I didn’t have it where I usually have it. This will be a good year for me to be motivated.”

Markus Rogan of Austria earned the bronze.

Mr. Peirsol’s last defeat in the 200 came at the 2000 Olympics, when he finished second to American Lenny Krayzelburg.

“I remember, I remember well,” Mr. Peirsol said. “I’m just glad (this time) to keep it in the family with Team USA.”

Mr. Lochte played it straight on the medals podium this time, with only a toothy white grin showing.

“Yeah, everyone is talking about that,” he said about his grill.

Mr. Phelps said he gave Lochte “a little crap” for not wearing the bling again, suggesting he buy a new grill with the gold-medal bonus money Lochte gets from USA Swimming and FINA, the sport’s governing body.

At the 2004 Athens Olympics, Mr. Lochte was second – again – to Mr. Phelps in the 200 IM.

Now, he’s broken through, with 17 months to go before the Beijing Olympics.

“My dreams are to become one of the best in swimming,” Mr. Lochte said. “Nothing can get in my way. Getting second won’t stop me.”

Kosuke Kitajima of Japan regained the 200 breaststroke world title he lost two years ago in Montreal. He did so without racing American rival and world-record holder Brendan Hansen, who withdrew from the preliminaries because of a virus.

Mr. Kitajima, the current Olympic and 2003 world champion, won in 2:09.80 – 1.19 seconds ahead of Aussie Brenton Rickard.

Mr. Kitajima was under Mr. Hansen’s world record through 100 meters, but couldn’t maintain the pace.

“I challenged myself to break the record more than winning this race,” he said. “In that, I am frustrated.”

Loris Facci of Italy took the bronze.

Leisel Jones of Australia easily completed a sweep of the women’s breaststroke events, winning the 200 by 4.10 seconds.

Ms. Jones led all the way and her time of 2:21.84 was third-fastest in history.

American Megan Jendrick and Kirsty Balfour of Britain tied for the silver in 2:25.94. American Tara Kirk, the 100 silver medalist, was last.

Libby Lenton of Australia defeated a loaded field in the women’s 100 freestyle, winning in 53.40 – the second-fastest time in history.

Marleen Veldhuis, under world-record pace at the turn, took the silver. Britta Steffen of Germany, the world-record holder, settled for the bronze. American Natalie Coughlin finished fourth.