NEW YORK (Reuters) - Defending champion Naomi Osaka advanced to the U.S. Open third round after Serbian qualifier Olga Danilovic withdrew ahead of their second-round match on Wednesday due to illness, tournament organisers said.

The Japanese third seed and world number 145 Danilovic, who was competing in her first U.S. Open main draw, were scheduled to be the day's second match in Arthur Ashe Stadium.