The stage is set for a star-studded final weekend at the Charleston Open as top four seeds Jessica Pegula, Ons Jabeur, Daria Kasatkina and Belinda Bencic all advanced to the semi-finals on Friday.

It is the first time since the 2012 Stuttgart Open that all four top seeds reached the final four in a WTA 500 event.

Pegula, the top overall seed and the only remaining American, used her commanding serving game to overwhelm 12th seed Paula Badosa 6-3 7-6 (8-6).

She ended up winning 80 per cent of her accurate first serves – compared to 57 per cent for Badosa – and it resulted in the Spaniard producing just one break point opportunity in the match, which she could not take.

Pegula will meet fourth seed and Olympic gold medallist Belinda Bencic next after her relatively comfortable 6-3 6-3 triumph against Russia's Ekaterina Alexandrova.

Switzerland's Bencic needed just 80 minutes to get the job done, creating 12 break point chances compared to Alexandrova's two, while winning the first three games of each set.

After coming into the tournament without consecutive wins since early January, reigning Wimbledon and US Open finalist Ons Jabeur looked back to her best in a dominant 6-0 4-1 (retired) drubbing of Anna Kalinskaya.

Jabeur is yet to lose a set in Charleston, and she will try to keep that the case when she faces Daria Kasatkina in her semi-final.

Kasatkina earned her spot in the final four with Friday's only three-setter, emerging victorious 6-7 (5-7) 6-4 6-2 against Madison Keys in just over two and a half hours.