Dominant Del Potro to meet Troicki in final

WASHINGTON (Reuters) - Juan Martin Del Potro extended his winning streak to 18 matches with a 6-2 6-1 destruction of Germany's Tommy Haas in the semi-finals of the ATP event in Washington on Saturday.

The second-seeded Argentine, who has won his last three tournaments in Stuttgart, Kitzbuhel and Los Angeles, overpowered Haas in one hour and 22 minutes.

Del Potro next plays unseeded Serb Viktor Troicki, who followed up his win over top seed Andy Roddick by beating Russia's Igor Kunitsyn 6-4 6-2

The 19-year-old Del Potro has not been beaten since the second round of Wimbledon in June and said he had almost forgotten how to lose.

"A little, yes, but tomorrow I can lose in the final so I have to keep going," Del Potro told reporters.

"Today I think Tommy was a little more tired than me and I played well. I have won a lot of matches, beat a lot of good players and got a lot of confidence.

"Tomorrow is the most important match. I have to play the final like it is my last."

Former world number two Haas had promised to mix up his game but once he was broken early in the first set, there only appeared to be one winner.

Del Potro's dominance from the baseline left the fourth seed frequently shaking his head.

After sealing a second break the world number 19 served out for the first set and a double-fault from Haas in the opening game of the second, put the Argentine completely on top.

Del Potro never looked like giving up the break and as Haas's head dropped, he cruised to victory.

NADAL STREAK

Only Rafael Nadal, who had a 32-match winning streak on his way to five title triumphs earlier this season, has won more consecutive matches and Haas said Del Potro would be one to watch at this month's U.S. Open.

"He will definitely be the dark horse," the German said. "The way he has been playing, he's probably feeling pretty good.

"It depends on the draw but he is one to reckon with. He is probably one of the youngest (top players) right now.

"If he continues this way you have to think he will be in the top 10 pretty soon, if not the top five."

Haas said he was unable to figure out the best way to play Del Potro.

"You can't really say what his weakness is," he added. "I wanted to bring him to the net a bit but I wasn't in a position to do that very often because I was on the defensive.

"I am pretty happy with the way I played this week, though. I just lost to a better player today."

Troicki reached his first ATP Tour final with a confident win over the unseeded Kunitsyn, wrapping up victory in one hour and 15 minutes.

(Editing by John O'Brien)