World No.4 Venus Williams survived a strong challenge from Canadian qualifier Rebecca Marino to progress to the third round at the US Open on Wednesday.
The nine-time Grand Slam winner beat the plucky teenager 7-6 (7-3) 6-3 in 91 minutes on Arthur Ashe Stadium to set up a clash with Luxembourg's Mandy Minella.
Williams, who is the No.3 seed at Flushing Meadows this year, is considered one of the tournament favourites despite having only just returned from a knee injury.
She had a comfortable win over Italian Roberta Vinci in the first round on Monday and would have been expecting a similar result against Marino, a qualifier who had never made it past the first round of a major before.
But the young Canadian, ranked 179th in the world, took it up to Williams in the first set to force a tie-breaker and take an early 3-1 lead.
But Williams responded with consecutive winners to take the next six points in a row to clinch the set.
In the second set Marino ran out of steam as Williams took over, breaking serve early and closing out the set 6-3.
Earlier on Wednesday, former world No.1 Ana Ivanovic breezed through her second-round clash with China's Zheng Jie.
The 21ist seed had no answer for Ivanovic's power from the back of the court as the Serbian raced through the match 6-3 6-0.
Italian sixth seed Francesca Schiavone also won through to the third round defeating compatriot Maria Elena Camerin 6-2 6-1.