By Simon Cambers

NEW YORK (Reuters) - Russian Nikolay Davydenko produced a stirring comeback as he recovered from two sets down to beat German Tommy Haas 4-6 6-7 6-3 6-4 6-4 to reach the U.S. Open semi-finals on Thursday.

The seventh seed was outplayed for two sets but Haas, who won back-to-back fifth-set tiebreaks to reach the last eight, tired as the match wore on and Davydenko held his nerve to reach the semi-finals in New York for the first time.

"I think I was lucky," Davydenko said.

"But it was tough, I was 5-2 (up in the final set) then break point and 5-4 and I didn't know what I could do, but I am happy to be in the semi-finals."

Focussing on Davydenko's forehand, Haas won four straight games to win the first set and looked on course for his first semi-final at Flushing Meadows when he took the second on a tiebreak.

But Davydenko refused to give in and one break in each set helped him to level the match.

After trading breaks at the start of the deciding set, Davydenko broke twice to lead 5-2 but Haas saved a match point and broke back and reduced the deficit to 5-4.

Haas then had two break points to level at 5-5 but Davydenko held on to set up a semi-final against either defending champion Roger Federer or American fifth seed James Blake.

CONFIDENT APPROACH

Until this year, Davydenko had won just one title on hard courts but having triumphed in the warm-up event in New Haven, he came into the event full of confidence.

"I didn't play so well on hard courts but now I prove I play better and better, I reach the semi-final of the U.S. Open on hard court, that, for me is already something special," Davydenko said.

Should Federer be his opponent in the semi-finals, Davydenko said he would have nothing to lose.

"I reached my best result in the semi-final," he said.

"So I just need to come to the court, not be nervous for the semis."

Haas admitted that fatigue had finally caught up with him, after his last-gasp wins over Robby Ginepri and Marat Safin on the way to the last eight.

"I think in the fifth set, for me, it was probably more physical than anything," he said.

"My body didn't feel as good anymore. I couldn't really do the small steps and was making too many unforced errors that way, couldn't cover the court as well as I did the first three, four sets."

Despite the defeat, Haas said he had to be satisfied with his efforts over the past ten days.

"Any time you make it to the quarters, you have to take something positive out of it," he said.

"But it's also tough. It's going to take a few days for sure to get over this loss, the possibility of getting to the semi-finals here at the U.S. Open.

"But I laid it out there as much as I could, fought until the last and even had two breakpoints to get back to 5-5 (in the fifth set). You never know what would have happened then."