Monica Puig raced into a commanding lead against Belinda Bencic before her momentum was halted by rain, which prevented both Sydney International semi-finals being completed on Thursday.

World number 94 Puig beat home favourite Samantha Stosur to reach the last four and the unheralded Puerto Rican raced into a 4-0 advantage in the first set against eighth seed Bencic on Show Court 1 before the heavens opened.

The unseeded Puig will need to carry on where she left off when play resumes at 10.30 local time on Friday as she goes in search of her second WTA title.

While Puig was comfortably in command of her semi-final, the other last-four encounter was on serve, with top seed Simona Halep leading Svetlana Kuznetsova 5-4 when play was suspended.

World number two Halep failed to hold in the first game of the match, but broke back immediately only to go a break down again at 3-2.

Kuznetsova then failed to hold in the eighth game at the Ken Rosewall Arena and Halep edged back in front before play was brought to a halt. 

All four quarter-finals in the men's competition will also have to be completed on Friday.