BRESSANONE, Italy – American Lance Armstrong admitted he is still finding his climbing legs after losing nearly three minutes to the favourites on the Tour of Italy's second day in the mountains.

Russian Denis Menchov won an uphill sprint to claim the Giro's fifth stage over 125km from San Martino di Castrozza to Alpe di Siusi on Wednesday as second-placed Italian Danilo Di Luca took the leader's pink jersey.

While Armstrong's Astana teammate Levi Leipheimer finished a handful of seconds behind the stage leaders, the seven-time Tour de France champion rode over the finish line 2min 58sec in arrears.

It was a performance that may leave some fans wondering whether Armstrong's aims for an eighth Tour de France title will hold water in July.

But the American, who only returned to racing in January following a two and a half year absence from the sport - and has only just recovered from a broken collarbone - admitted he was happy limiting his losses.

And the 37-year-old said he would look forward to the second half of the Giro to possibly aim for his maiden stage win on the race.

"We just started to ride our tempo and try to limit the losses," said Armstrong after Wednesday's stage.

"Like I said in the beginning, the first half is not going to be my half. I have to ride into the race and get my condition back after the accident. I cannot expect to be in the front.

"I didn't come in with any big illusions. I knew I'd be minutes behind the best guys. It was a matter of finding the right rhythm, you find your threshold and hold it there. We'll see what happens in the second half of the Giro."

After two days of climbing in the spectacular Dolomites mountains, 2007 champion Di Luca leads Sweden's Thomas Lovkvist by five seconds, with Australian teammate Michael Rogers at 36.

Astana leader Leipheimer is fourth overall at 43, with three of his fellow favourites - Menchov, Ivan Basso and Carlos Sastre - at 50, 1:06 and 1:16 in arrears respectively.

Menchov, Basso and Sastre have each won major three-week Tours and had been looking to distance their rivals as much as possible in the mountains before stage 12's 60km time trial in the second week.

Wednesday's summit finish was the last real climbing test, and last summit finish, until the 237km ride from Pergola to Monte Petrano on stage 16.

Armstrong believes the days in between, a mixture of flat and medium-mountain stages, could give him ideas about going for his maiden Giro stage win.

"This is interesting, because this is the last uphill finish until Petrano - there are a lot of days that are more tranquilo, then we have the big time trial, then we head south, so there will be more opportunities," he added.

"It's a beautiful race, but we all knew that, especially with the 100-year anniversary. There's a special atmosphere on the side of the road and within the peloton."