The 1997 champion needed the special invitation because she didn't register by the deadline last month, while she was recovering from ankle surgery in May.

Hingis, formerly ranked No. 1, missed the French Open and Wimbledon this year, the first Grand Slam tournaments she missed since turning pro in 1994.

She returned to action this week at the Rogers AT&T Cup in Montreal.

Also granted wild-card entries into the main draw of the Open were Corina Morariu, Mashona Washington, Ally Baker, Bea Bielik, Ashley Harkleroad, Alexandra Podkolzina and Sarah Taylor.

The U.S. Open starts Aug. 26.