Madison Keys and Karolina Pliskova edged into the fourth round at the US Open, as Agnieszka Radwanska and Jelena Ostapenko bowed out.

Keys recovered from a slow start to get past Elena Vesnina in a match that finished on Sunday morning at Flushing Meadows.

World number one Pliskova saved a match point as the Czech battled past Zhang Shuai.

As Elina Svitolina also progressed, Radwanska and Ostapenko were beaten.

KEYS GETS THROUGH

Keys reached the fourth round in New York for the third consecutive year, overcoming Vesnina 2-6 6-4 6-1.

The American 15th seed is considered a contender at the year's final major, and 44 unforced errors from Vesnina helped Keys through.

Next up for Keys is fourth seed Svitolina, who was too good for Shelby Rogers 6-4 7-5.

PLISKOVA BATTLES

Pliskova had to save a match point to progress, battling past Zhang 3-6 7-5 6-4.

Last year's runner-up, Pliskova will next face Jennifer Brady after the American overcame Monica Niculescu 6-3 4-6 7-6 (7-3).

RADWANSKA, OSTAPENKO UPSET

The 10th-seeded Radwanska went down to Coco Vandeweghe 7-5 4-6 6-4 after almost three hours.

French Open champion Ostapenko also bowed out, brushed aside by Daria Kasatkina 6-3 6-2 before a frosty handshake between the pair at the net.

Progressing to the fourth round were Lucie Safarova and Kaia Kanepi.