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Laura Robson's hopes of breaking into the world's top-50 for the first time suffered a setback when she was knocked out of the China Open in round two.

The 18-year-old Briton was defeated 7-5 6-3 by Spain's Lourdes Dominguez Lino.

An evenly matched opening set went with serve until Dominguez Lino converted the first break point of the contest in the very last game.

Quick breaks saw the Spaniard take a 3-1 lead in the second and she wrapped up victory in just over 90 minutes.

Robson, who won Olympic mixed doubles silver with Andy Murray this summer, has risen from world number 131 to 60 in a year and became the first British woman to reach a WTA final since 1990 when she was a runner-up at the Guangzhou Open in September.

She also reached the fourth round of the US Open, before losing to defending champion Samantha Stosur.

Robson returns to action at next week's HP Open in Osaka, Japan.

Elsewhere in the women's event in Beijing, Chinese star Li Na brushed aside in-form Russian Nadia Petrova 6-1 6-2 to progress to the last 16.

It was the 2011 French Open champion's first win against Petrova, who won last week's Pan Pacific Open in Tokyo, in seven attempts, a timely boost as she aims to qualify for the WTA Championships - featuring the world's top eight - in Istanbul later this month.

Frenchwoman Marion Bartoli, two places behind Li in the race to qualify, German fifth seed Angelique Kerber and defending champion Agnieszka Radwanska also progressed.

In the men's event, an out-of-sorts Novak Djokovic, playing his first match since losing to Andy Murray in the US Open final, required three sets to defeat German qualifier Michael Berrer.

The world number two took the first set with ease but lost the second on a tie-break after several unforced errors against the left-hander, ranked 123rd in the world.

But the Serb improved to take the decider and complete a 6-1 6-7 (3/7) 6-2 victory as he chases a third China Open title in three appearances, having won it in 2009 and 2010 before missing last year's event because of injury.

Third seed Jo-Wilfried Tsonga also progressed but fellow Frenchman Julien Benneteau was forced to retire shortly into the second set against Italian Andreas Seppi.