Washington, Aug 9 (DPA) Andy Roddick escaped in a nail-biting semi-final finish, holding off unseeded American John Isner 6-7 (3-7), 6-2, 7-5 to set up a title match at the Legg Mason Classic with holder Juan Del Potro.

The number two Argentine booked his place in an afternoon struggle with fatigue in steamy conditions to reach a second straight Washington final 7-6 (7-2), 6-3 over fellow South American Fernando Gonzalez.

Roddick and upcoming Isner - who managed more than 20 aces-battled for more than two and a half hours Saturday to establish superiority, with the underdog giving as good as he got from three-time Wimbledon finalist Roddick.

Roddick, the top seed with three Washington titles in his pocket, didn't get out of danger until the last moment as an Isner net bounce landed out to give Roddick a pair of break points in the 11th game of the final set.

Isner saved one but Roddick secured the break for 7-5 on the second from an error and then served out the win a game later with a down-the-line winner to the empty corner.

'I played well, but John kept coming up with the goods,' said Roddick. 'The final will be tough as Del Potro really drives the ball and can pull the trigger from either side.