Clijsters has won 26 consecutive first-round matches at Grand Slam tournaments.
The No. 2-seeded Clijsters fell behind 4-0 in the second set, and Arn served for the set at 5-4. But Clijsters broke serve there, and again in the match's final game. Clijsters said she was "just glad to finish that second set off and not let it go three sets."
The Belgian also said the left hip that bothered her at a tuneup tournament this month "feels much better."
A year ago at Flushing Meadows, Clijsters became the first wild-card entrant to win a women's singles title at a Grand Slam tournament.