NEW YORK: Second seed Dominic Thiem staved off a spirited fightback from Marin Cilic to beat the former champion 6-2 6-2 3-6 6-3 on Saturday and reach the fourth round of the US Open. Austrian Thiem had won both his previous meetings with the 31st seeded Croat and quickly stamped his authority on the evening's final match on the Arthur Ashe Stadium court with two service breaks in each of the first two sets. Cilic found his range to win the third, breaking serve for the first time, but world No. 3 Thiem saved five break points in the fourth set and sealed the match when his opponent found the net on a return. Thiem will next meet Canadian Felix Auger-Aliassime, who beat France's Corentin Moutet 6-1 6-0 6-4.