Li was a top-10 seed when she lost in the first round at Flushing Meadows in each of the previous two years.
Marion Bartoli of France, seeded 11th, defeated American Jamie Hampton 6-3, 7-6 (5), and 19th-seeded Nadia Petrova of Russia advanced with a 6-3, 7-6 (3) win over Jarmila Gajdosova of Australia.
It was a rough first day for the German women, with 16th-seeded Sabine Lisicki and 18th-seeded Julia Goerges both losing.
The American men got off to a good start with wins by two wild cards, 32-year-old James Blake and 19-year-old Jack Sock.
Sock took a two-set lead over Florian Mayer before the No. 22 seed quit after feeling faint and dizzy. Sock won the U.S. Open boys championship in 2010, becoming the first American to take that title since Andy Roddick, 10 years earlier. He came into this year’s tournament ranked 248th and without a win over a top-50 player.
Sock was ahead 6-3, 6-2, 3-2 when Mayer retired.
Blake reached the second round of a Grand Slam event for the first time this year, beating Lukas Lacko 7-5, 6-2, 3-6, 6-3. He had needed a wild card to make his 12th appearance at the Open after his ranking fell out of the top 100. He hadn’t lost in the first round at Flushing Meadows since his debut in 1999.
Top-seeded Roger Federer plays American Donald Young in the night session Monday.
Also playing in Arthur Ashe Stadium are No. 3 Maria Sharapova, against Melinda Czink of Hungary, and No. 23 Kim Clijsters, opening the final tournament of her career with a first-round match against American Victoria Duval. Clijsters missed last year with an injury, but has won the tournament the past three times she’s entered — in 2005, 2009 and 2010.
AP National Writer Eddie Pells contributed to this report.
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