The national men’s water polo team secured its first-ever semifinal berth in world championship competition yesterday after defeating the USA 4-2 in a quarterfinal encounter at the FINA World Championships in Barcelona. Greece will now meet Hungary, a water polo powerhouse, in their semifinal tomorrow night. Hungary registered a convincing 13-5 win over Slovakia for its place in the last four. Greece had defeated another giant, Russia, a day earlier, following a nail-biting penalty shootout to break their quarterfinal deadlock. The Greek team’s excellent defensive play proved instrumental in the victory over the Americans, who managed to capitalize on just one of nine attacks with an extra player in the pool. (In water polo, teams are penalized by temporary sending off a player for infringements.) A solid American defense made scoring difficult. It took the determined Greek team a full 14 minutes to register its first goal, courtesy of Argyris Theodoropoulos, who came on as a substitute and scored with his first touch of the ball. The Americans had opened the scoring earlier with an extra player in attack. Theodoropoulos put the Greek team ahead in the game’s third quarter. With a one-goal advantage late in the game, Greece, which bolstered its defense to avert an equalizer, managed to go up 3-1 on the counterattack with a thunderous long-range shot from Thodoris Hatzitheodorou. A second American goal that narrowed the difference seemed to do nothing to alarm the Greek side, which secured its victory with a fourth goal, 49 seconds before time, from Tassos Schizas. The women’s team will meet Germany tonight in a game to determine ninth place.