Top-ranked Novak Djokovic defeated Grigor Dimitrov of Bulgaria 6-2 6-4 to reach the China Open semi-finals and extend his winning streak at the tournament to 22 matches on Friday.

Djokovic dropped serve twice in the second set, but the fifth-seeded Dimitrov was unable to consolidate either break, making costly errors to give the breaks right back.

Djokovic also ended Dimitrov’s run at Wimbledon this year with a four-set victory in the semi-finals.

The Serb next plays sixth-seeded Andy Murray, who beat US Open champion Marin Cilic 6-1 6-4.

Djokovic, who has an incredible 100 per cent record at the $US5.4 million ($A5.84 million) tournament was again highly emotional on the Diamond Court at China’s National Tennis Centre, smashing his racket twice in the second set in frustration.

The Serb broke his Bulgarian opponent’s service twice in the first set, after saving three break points in the third game.

He appeared to be heading for a routine victory at 5-3 and serving for the match in the second set, but Dimitrov broke serve to temporarily halt Djokovic’s advance.

But Djokovic took the next game and wrapped up his victory in 90 minutes.

He described his refusal to hand Dimitrov his serve early on as a “big” moment, and was pleased with his performance.

“That was pretty big. I mean, we both started a bit rusty on the court, lot of unforced errors. So it took a little bit of time to get into the groove, to get into the rhythm,” Djokovic said.

Meanwhile, Murray crushed his opponent in the first set, breaking serve three times. He was then forced to wait until the final game of the second set to break again and clinch victory.

The 27-year-old Scot is bidding for a second consecutive title in China after he won in Shenzhen last weekend.

He is desperately chasing points as he pushes to qualify for the ATP World Tour Finals next month, which features the top eight men’s players.

Only five berths are available as the world’s top three players – Djokovic, Rafael Nadal and Roger Federer – have already confirmed their place for the London tournament.

Murray is in ninth position and is aiming to pick up points in Beijing and at the Shanghai Masters next week.

The duel between Murray and Djokovic Saturday will be a re-match of their epic US Open quarter-final, which Djokovic won 7-6 (7-1) 6-7 (1-7) 6-2 6-4.