Defending champion Novak Djokovic swept aside Jo-Wilfried Tsonga 6-2, 7-5 on Saturday, as a mouthwatering Shanghai Masters title showdown loomed against world number one Rafael Nadal.

The powerful Tsonga came into the semi-final at the Qizhong Tennis Center with a miserable run of eight consecutive defeats against the top seed, but had not dropped a set all week.

However, he landed just 46 percent of first serves in an ultimately one-sided first set, and despite a better performance in the second he cracked in the 12th game as Djokovic completed a straight-sets win.

"It's important for me to get into another final," said Djokovic, who lost his cool midway through the second set over a couple of line calls before he found his focus again.

"(My serve) was very controlled, very efficient... I was trying to open up the court and move him around. I know he likes to have targets, he likes to play from the backhand corners so I tried not to let him into that comfort zone."

Tsonga made the worst possible start in windy conditions as Djokovic threatened to run away with the match.

The Serbian, 26, broke to love in the second game, helped by two double faults, and had a break point to establish a 4-0 lead as Tsonga struggled to gain a foothold.

The seventh seed dug deep, securing a break of his own to peg Djokovic back to 3-2, but his form then dipped again and he lost the next three games.

A more balanced second set involving a break apiece looked to be heading towards a tie-break, but the Serb secured a decisive break in the 12th game, claiming victory on his second match point.

Tsonga, 28, who has admitted this week he is not quite 100 percent fit after knee problems forced him to miss the US Open, won just 13 of 31 points at the net.

"I didn't serve good enough in the first set to cause him some trouble, but after that I played better and better," he said. "I served better. I was more into it. So for him it was a bit more trouble, but it's still 7-5."

Nadal, who re-claimed the top ranking this week, plays Argentine sixth seed Juan Martin del Potro in the second semi-final later Saturday, seeking to set up a re-match of Sunday's China Open final in Beijing, won by Djokovic.

The Spaniard has enjoyed one of the best seasons of his career, winning 10 titles including the French Open and the US Open, and is seeking a record sixth Masters title in a single season.

Nadal and Djokovic are among three players who have already secured their places at next month's elite World Tour Finals, featuring the season's top eight players.

Tsonga and Del Potro are among those hoping to secure one of the remaining five places. -- AFP