Bold Armstrong fails to break Greipel grip

An audacious Lance Armstrong attack failed to break Andre Greipel's stranglehold on the Tour Down Under on Friday as the German claimed his third stage win in emphatic style.

Armstrong and RadioShack team-mate Tomas Vaitkus broke forward with about 16 kilometres (10 miles) to go, but were caught by the pack in hot and windy conditions near the end of the 150-kilometre stage four.

Greipel, the 2008 champion from Germany, put on a trademark powerful sprint to cross ahead of Australians Robbie McEwen and Graeme Brown and stretch his overall lead to 20 seconds.

"That was as hard as I can go," said an exhausted Armstrong, who finished some 17 seconds behind the winner.

"Tomas went and kept going and kept going. I turned around and it was just the two of us. It was a good effort, maybe not the best outcome."

Greipel crashed into a parked police motorbike during last year's race, dramatically ending his title defence and condemning him to four months out with shoulder surgery.

He was jubilant after Friday's win but said it was too early to start celebrating a second Tour Down Under victory with the event's most challenging climb, the notorious Willunga Hill, looming on Saturday.

"Today's race is over, but not tomorrow's," Greipel said, praising his HTC-Columbia team. "Everyone is looking out for us but if the team works we can be successful. We deserve the wins because we always ride from the front."

Greipel now holds a 20-second advantage overall from McEwen, with Team Sky's Greg Henderson four seconds further back and world road champion Cadel Evans 26 seconds adrift.

Armstrong, who is 29th overall, described the tall, lean German as "unbeatable" in a straight sprint after he also pounced for victory on Tuesday and Wednesday, with Portugal's Manuel Cardoso the only other stage winner.

The 38-year-old American, who has drawn massive crowds as he bids to extend his record seven Tour de France wins, said he progressing well in the second year of his comeback.

"I feel better than I thought but I still don't think I have the legs to go with the best, best guys tomorrow," he said.

"I think (Alejandro) Valverde, Cadel (Evans) will be strong and a few other guys. I'll be just off that.

"It feels different than last year, it feels more comfortable both pedalling but also in the bunch, positioning, feeling the race. I feel my condition is more advanced, I feel a little lighter."

He added that the Tour Down Under, which attracts hundreds of thousands of fans and a world-class field, seemed to be getting more competitive.

"I think you've got a race that's been around longer, continues to get big international exposure and has new teams, new sponsors that have high expectations, so when you have that guys train harder," he said.

"Back in the day guys started training in January. Now they start training harder and harder in November. I think it's a good preparation but I wouldn't want it to get any harder."

The Tour Down Under, the southern hemisphere's biggest race, is held over six stages on 800 kilometres of road around Adelaide and closes on Sunday.