Washington, DC -- (Sports Network) - Argentina's Juan Martin del Potro continued his sizzling play of late with an easy straight-set victory over Germany's Tommy Haas in the semifinals of the Legg Mason Tennis Classic.

The second-seeded del Potro cruised to a 6-2, 6-1 triumph for his 18th straight match victory. He will play in an ATP final for the fourth straight tournament, having captured titles in Stuttgart, Kitzbuhel and Los Angeles since a second-round loss to Stanislas Wawrinka at Wimbledon.

During the incredible run, del Potro has dropped only two sets.

Haas was no match on Saturday. The fourth-seeded veteran held a 2-1 lead in the first set, then watched del Potro reel off nine straight games to take total control.

Del Potro finished off the match in an hour and 22 minutes. He will try for his fourth straight ATP singles title on Sunday against unseeded Viktor Troicki of Serbia.

Troicki dispatched Russia's Igor Kunitsyn in straight sets, 6-4, 6-2, in a match that lasted just over one hour, 15 minutes Saturday evening.

Troicki reached the semis with a stunning come-from-behind quarterfinal victory over American Andy Roddick. The top-seeded Roddick, who lost to del Potro in last week's Los Angeles final, won the first seven games on Friday before Troicki pulled off the surprising 0-6, 6-2, 6-4 triumph.

Kunitsyn, meanwhile, was a 6-4, 6-1 quarterfinal winner over Indian qualifier Somdev Devvarman.

This week's titlist will collect $80,650.