Top seed Yanina Wickmayer continued her run at the Carlsbad Classic after dispatching of Kristie Ahn in straight sets on Thursday.

Wickmayer saw off Ahn 7-5 6-3 as the Belgian booked a spot in the quarter-finals of the WTA 125k Series tournament in California.

Six breaks of serve against her American opponent were enough to see Wickmayer win through from the second round after one hour, 35 minutes on court.

Awaiting the 2009 US Open semi-finalist in the quarters is Catherine Bellis.

Bellis needed more than two hours to overcome fellow American Katerina Stewart 6-2 5-7 6-4.

Serbian third seed Bojana Jovanovski had no such luck, beaten by Marina Melnikova in three sets.

Jovanovski was expected to join Wickmayer in the last eight but instead she was upstaged 7-5 4-6 6-4.

Melnikova's surprise win earned her a meeting with Jennifer Brady, who defeated Elitsa Kostova 7-5 3-6 6-4.