* Stepanek and Berdych grind out five-set victories
* Croat Karlovic's world record 78 aces not enough
* Hosts must win Saturday's doubles to stay alive (updates after second rubber)
POREC, Croatia, Sept 18 (Reuters) - Czech Republic took a 2-0 lead in their Davis Cup semi-final against Croatia on Friday after Radek Stepanek battled for six hours to beat Ivo Karlovic and Tomas Berdych also won in five sets against Marin Cilic.
Stepanek put the visitors ahead by overcoming Karlovic 6-7 7-6 7-6 6-7 16-14 in a marathon opener in which the 82 games played equalled the highest number in a Davis Cup rubber since the introduction of the tiebreak in 1989.
The games total was just three short of the overall record for a World Group tie after world number 17 Stepanek achieved the key break of serve in the 29th game of an epic fifth set.
Karlovic, the tallest man in professional tennis, fired down a world record 78 aces but it was not enough to win an extraordinary match that had the fans on the edge of their seats at the Zatika Arena in the northern Adriatic town of Porec.
"I have no words right now, it was like a lottery and I managed to seize my chances," said Stepanek after the fourth longest Davis Cup match, which lasted five hours 59 minutes.
"It was a long and exhausting match but when you play for your country it's worth it. It wouldn't matter if it lasted for another few hours," he told Croatian TV.
In the second rubber, Berdych needed three hours and 47 minutes to beat 15th ranked Cilic 6-3 6-3 3-6 4-6 6-3.
HARD MATCH
"It was a very hard match... I played great at the start, but Marin came back," world number 18 Berdych told Croatian television. "With huge help from our fans, I managed to beat him and I think this was one of the best matches I have ever played.
With the Czechs needing just one more point to reach the final, Croatia must win Saturday's doubles match to keep the tie alive for Sunday's reverse singles rubbers.
Czechoslovakia won the Davis Cup in 1980 with a 4-1 triumph over Italy but Czech Republic have never reached the final.
Spain lead Israel 2-0 after Friday's singles rubbers in the other semi-final being played in Murcia.
Stepanek and Karlovic were exhausted after a thrilling, see-saw encounter accompanied by the sound of bugles and drums in which the Croat failed to convert five match points.
The big-serving Karlovic obliterated the all-time aces record of 59 held by American Ed Kauder since 1955 but said it was no consolation for losing.
"This is a tough defeat but I did the best I could," said the world number 31. "I was a bit disappointed by the fact that too few people attended the event and that the visiting crowd outshouted the local supporters."
Croatia coach Goran Prpic was disappointed only a handful of home fans turned up at the 3,700-capacity arena.
"Luck has turned its back on us today..." he said. "We played great tennis but the atmosphere was as if we played in the Czech Republic and in such tough matches it can prove to be a decisive factor."
(Reporting by Zlata Zsolnay, editing by Ken Ferris and Tony Jimenez
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