SYDNEY (AP) -- In new shoes shimmering with droplets of 24-carat gold, Michael Johnson is aiming for the 43-second barrier and maybe a U.S. sweep in his Olympic 400-metre farewell.

 Far more relaxed than he was in his successful quest for an unprecedented double gold in the 200 and 400 four years ago in Atlanta, Johnson told reporters Tuesday that there are two more milestones in running history he'd like to achieve.

 He wants to be the first man to repeat as 400-metre Olympic champion, and he wants to break the 43-second mark. Johnson set the world record of 43.18 seconds at the 1999 world championships in Seville, Spain.

 For Johnson, who turned 33 last week, his final Olympic Games would be the perfect stage to break the 43-second barrier.

 "I don't know when it's going to come, but I'm running out of time," he said. "I always perform best at the big championships -- the world championships, the Olympic Games. All of my world records have come at the world championships, the Olympics, major championships.

 "So certainly if the weather co-operates here, the opportunity may be here to break 43 seconds. I think I'm in shape to do it right now. I think I'm capable of doing it right now. But it takes more than that."

 He doesn't want 43.18 to be his 400-metre legacy.

 "I'm very proud of it, but I just feel that I can do much better than that," he said. "I would like to have my 400-metre world record in my mind equal to what my 200-metre record means. It would be something so far out there it's hard to understand."

 That 19.32-second performance in winning the 200 gold in Atlanta stunned a packed stadium and the track and field world. It also made him the first to win the 200 and 400 at the Olympics.

 Johnson intended to try to double again this year, but pulled up with a hamstring injury in his much-hyped showdown with fellow American Maurice Greene in the 200 finals at the U.S. trials. Greene also pulled up lame, and neither will be in the 200 in Sydney.

 The injury has healed, and Johnson said he's run better in recent training than he did in the days leading up to his world-record run a year ago.

 Johnson said he is relieved not to be facing the grueling challenge again, and he enjoys not being "the story" of the Olympics this time.

 "I'm very happy with my situation," he said. "I'm very happy to be here running the 400 and I'll be running the 400 in the relay. I've done the 200. I've done the 400. I wouldn't want to not be here, but if I had to choose an event to be here in, it would be the 400.

 "I'm happy to be here without all of the pressure of running the 400 and then go back and doubling in the 200. That's double the pressure. This is my last Olympics and I wanted to be able to enjoy it a lot more."

 Johnson brushed aside suggestions that he is such an overwhelming favourite that everyone else will be running for silver.

 "I heard Alvin Harrison say the other day that he's running for a gold medal," Johnson said, "and he came down here and ran 44.18. (Sept. 8 in Brisbane) ... Nobody's going to train that hard to come down here and give me anything. I've got to go out there and earn it."

 Harrison has been running so well that Johnson believes there's "a very good chance" of a 1-2-3 U.S. finish, with the third American, Antonio Pettigrew, the biggest question mark.

 "The way that Alvin Harrison is running, he certainly is going to be a medal contender," Johnson said, "and with all the experience Pettigrew has, you just never know. With Pettigrew, it depends on the race."

 The slower the pace in the first 200 metres, the better the chance Pettigrew will be able to contend, Johnson said.

 At the end of his news conference at Nike's Olympic headquarters, Johnson briefly displayed one of his new shoes. With genuine gold, it glittered even more brightly than the ones he wore when he set the 200 world record in Atlanta.

 When Johnson won the 400 at the U.S. Trials in Sacramento in July, he threw his shoes into the crowd. He's not sure he'd do that if he wins in Sydney.

 "They're a little more expensive," he said with a smile, "but somebody might be lucky enough."