Roger Federer and Novak Djokovic, the top two players in the world, set up a showdown for the Cincinnati Masters title after cruising to semi-final victories on Saturday.
The gap between the leading four, which also contains Rafa Nadal and Andy Murray, and the chasing pack was again evident as Djokovic beat Argentine Juan Martin del Potro 6-3 6-2 before Federer saw off fellow Swiss Stanislas Wawrinka 7-6 6-3.
World number one Federer is chasing a fifth title in Cincinnati while Djokovic is hoping to claim his first at the Ohio venue.
In the women's draw, China's Li Na has beaten Venus Williams playing in her first semi final for two years.
Na's opponent in the final is the German, Angelique Kerber, who beat the Czech, Petra Kvitova, in the other semi final.