BUENOS AIRES, Sept 19, 2008 (AFP) - David Nalbandian and teenage hotshot Juan Martin Del Potro gave Argentina a 2-0 lead over Russia in their Davis Cup semi-final here on Friday.

Nalbandian eased past Igor Andreev 7-6 (7/5), 6-2, 6-4 before 19-year-old Del Potro took his summer streak to 24 wins in 25 matches by stunning world number six Nikolay Davydenko 6-1, 6-4, 6-2.

Victory for Agustin Calleri and Guillermo Canas over Igor Kunitsyn and Dmitry Tursunov in Saturday's doubles will put Argentina into only their third Davis Cup final.

They lost to Russia in the 2006 title match and the US in 1981.

If Argentina come through, they will likely meet Spain, who lead their semi-final against defending champions America 2-0 in Madrid, in December's final.

They would also have home advantage.

World number seven Nalbandian wrapped up victory over the 19th-ranked Andreev in two hours and 23 minutes after making the most of a controversial umpiring decision when he trailed 2-4 in the first set tiebreak.

The Argentinian's big forehand hit the netcord and was called out but umpire Carlos Bernardes ruled the point to be replayed. Nalbandian took it and then won four of the next five to turn the set round.

'That point was crucial,' said Nalbandian who has now won all 16 Davis Cup matches he has played at home.

'I hit a nice shot (on the replayed point), I felt different in the tiebreak, and I could turn it around.'

Andreev, standing in for the unavailable Marat Safin, also saw that point as the turning point.

'I thought the ball was out, but the chair umpire said it was good, we had to replay the point, and after that everything went wrong.'

Del Potro, who won four titles on the American hardcourt swing in the run-up to the US Open, was never troubled by the experienced Davydenko and stormed into a 6-1, 4-1 lead before the Russian briefly fought back.

'I played unbelievably,' said Del Potro.

'At the end of the second set I was nervous, but with these people it?s so easy to play when you?re nervous. But we?re not in the final yet, so we need to concentrate on winning one more.'