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By Matt Majendie

NEW YORK (Reuters) - Defending champion Kim Clijsters eased past close friend Ana Ivanovic 6-2 6-1 to reach the last eight at the U.S. Open Sunday.

The match between the two former world number ones had been hotly anticipated at the Arthur Ashe Stadium but Ivanovic, who had shown signs of her best form in the earlier rounds after a difficult 18 months, seemed to lack confidence against the second seed.

Belgian Clijsters broke the Serbian's serve three times in the first set and repeated the feat in the second set for a comfortable passage into the quarter-finals.

(Editing by Clare Fallon)