CINCINNATI (Ohio), Aug 19: Roger Federer and Novak Djokovic, the top two players in the world, set up a showdown for the Cincinnati Open 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 No 1 Federer is chasing a fifth title in Cincinnati while Djokovic is hoping to claim his first at the Ohio venue.

The Serb has lost in the final three times including last year when he retired injured in the second set against Murray and in 2009 when he was beaten by Federer.

Djokovic avenged his defeat by Del Potro in the bronze-medal match at the London Olympics earlier this month when he powered into his 22nd Masters 1000 final.

A tight first set turned in Djokovic’s favour when sixth seed Del Potro, who was unable to capitalise on any of the six break points he had in the match, double-faulted to let his opponent go 4-2 ahead.

It was relatively straightforward in the second set after Djokovic, who won last week’s Toronto Masters crown, took advantage of some loose returns to break for a 2-1 lead.

Federer has a 15-12 advantage in matches with Djokovic and won their last meeting in the Wimbledon semi-finals last month.

Federer, who won 75 percent of his service points, has already won titles this season at Wimbledon, Indian Wells, Madrid, Rotterdam and Dubai and will look for another psychological boost ahead of the US Open later this month.

China’s Li Na, meanwhile, defeated an injured Venus Williams 7-5, 3-6, 6-1 to reach the final of the women’s event and set up a meeting with German Angelique Kerber.

Wimbledon semi-finalist Kerber came through a gruelling 6-1, 2-6, 6-4 win over Czech Petra Kvitova to reach her fourth final of the year and her biggest yet.Earlier, Williams, playing in her first semi-final since the 2010 US Open, was limited in her serve speed which was hovering around a slow 75 mph mark after picking up a back strain shortly before the match begun.

Kerber’s rise to seventh in the rankings this year, based on her rock solid defence, has included wins at the Paris indoors and Copenhagen events but her test against Li will be the perfect preparation for Flushing Meadows.

In an all-left-hander clash, the German dominated the opening set with Kvitova making a series of unforced errors but the gritty Czech dug deep to take the contest to a third, making full use of her powerful serve.

Kerber, though, swiftly regained her rhythm to race into a 5-2 lead in the decider against an exhausted looking Kvitova.

The German was then broken as she served for the match before sealing the contest just before it reached the two hour mark on her next service game.

Results (prefix number denotes seeding): Men’s singles: Semi-finals: 1-Roger Federer (Switzerland) bt Stanislas Wawrinka (Switzerland) 7-6 (7-4), 6-3; 2-Novak Djokovic (Serbia) bt 6-Juan Martin Del Potro (Argentina) 6-3, 6-2.

Women’s singles: Semi-finals: 5-Angelique Kerber (Germany) bt 4-Petra Kvitova (Czech Republic) 6-1, 2-6, 6-4; 9-Li Na (China) bt Venus Williams (US) 7-5, 3-6, 6-1.—Reuters