San Martino di Castrozza, Italy  - Seven-time Tour de France winner Lance Armstrong on Tuesday looked impressive for most of the day, but lost valuable ground on the last kilometre as Danilo di Luca won the fourth Giro d'Italia stage.

The Astana team captain fell back to sixth in the overall standings - 28 seconds behind Swedish Columbia cyclist Thomas Loevkvist, who took over the overall leaders' jersey.

Di Luca, who won the 162 kilometre-long stage from Padua to San Martino di Castrozza ahead of compatriots Stefano Garzelli and Franco Pellizotti, is two seconds behind the Swede.

The LPR Brakes cyclist Di Luca, who won the race in 2007, is one of the favourites to lift the title again and was in top form as he won in four hours, 15 minutes and four seconds.

For Armstrong the first of six mountain stages was the most difficult stage he has faced since his last Tour de France win in 2005.

As expected sprint-star Alessandro Petacchi, who won the last two stages of the race, had no chance and had to give up the leaders' jersey to Loevkvist.