NEW YORK, Aug 30 (Reuters) - World number seven Andrey Rublev made short work of veteran qualifier Ivo Karlovic in the U.S. Open first round on Monday, beating the tricky Croatian 6-3 7-6 (3) 6-3 to set up a clash with Pedro Martinez. The Russian came into the year"s final Grand Slam having reached the Cincinnati title clash and made a blistering start on Grandstand, winning the opening three games of the match before taking the first set in style. The 42-year-old Karlovic, the oldest U.S. Open qualifier in the Open Era, launched his comeback in the second set but Rublev held his nerve in the tiebreak, which he claimed with a forehand winner, before shifting gears in the final set. After racing to a 5-3 lead, the 23-year-old former Flushing Meadows quarter-finalist closed out the match on the back of his steady service game, forcing a backhand error from the towering Karlovic on match-point. Rublev returned superbly throughout the match, effectively dealing with his 6-foot-11-inch opponent"s fiery serve as he converted two breakpoints and fired 27 winners in a solid performance to begin his bid for a maiden Grand Slam title. Up next for Rublev is Spaniard Martinez who was made to work hard by Australian James Duckworth before sealing a 4-6 4-6 7-6(7) 6-2 6-2 win.