Former world number one Jelena Jankovic has knocked out home favourite Madison Keys in the first round of the US Open at Flushing Meadows.

Eighteen-year-old Keys is considered to be the future of American women's tennis, but she was overpowered by her experienced opponent, who was a finalist at this tournament in 2008.

Jankovic gained a crucial break in the second game of the first set, and then saved a break point on her own serve to take a 4-1 lead in the opener, which she took at 6-3 at the third attempt.

Another early break in the second set helped the Serbian ninth seed firmly establish her advantage and shewent on to complete a comfortable 6-3 6-4 victory in an hour and eight minutes.

Jankovic will face Russian Alisa Kleybanova in the second round.