Beijing - World number one Novak Djokovic on Saturday warned a resurgent Rafael Nadal that he won't give up the top spot without a fight as he prepares to defend his China Open crown.
Nadal has been in sizzling form this season - moving to third on the all-time list of Grand Slam champions after claiming victory over Djokovic at this month's US Open - and the Spaniard could become the world number one for the first time since July 2011 with a good performance in Beijing.
Djokovic acknowledged that the current number two has had a more consistent season, but said he is confident he can reproduce the form in Beijing which has seen him unbeaten in three visits to the tournament, following up wins in 2009 and 2010 with victory over Jo-Wilfried Tsonga in last year's final.
"As long as there is a chance, I will fight for that top spot," he said at the dual ATP and WTA event, which is being staged at Beijing's Olympic Park.
"But, again, with no doubt he has the best results this year. This year he's been the best player in the world. I have been having ups and downs throughout this year. But still it was a quite good season for me, but it's not over.
"I want to focus on this week's China Open because this is where I traditionally play well, and I would like to have another successful week."
Djokovic is the top seed in Beijing, ahead of number two Nadal, the ATP said on its website Saturday.
The reigning champion will play Czech Lukas Rosol, who is ranked 46th in the world, in his opening game, while Nadal will face a qualifier who is yet to be named.
The men's competition of 32 players is still at the qualification stages, and organisers are yet to announce the tournament schedule.
The women's tournament, which has 64 competitors, began on Saturday with former champion Agnieszka Radwanska saying that she wanted to emulate her 2011 success.
The Polish world number four is seeded third in Beijing, and arrives on the back of winning the Korea Open last week, before crashing out of the Pan Pacific Open in Tokyo in the quarter-finals on Thursday.
The 24-year-old is up against a strong women's field in China, including world number one Serena Williams, and Victoria Azarenka, the current world number two and reigning China Open champion.
But Radwanska said she was relaxed despite the tough competition, particularly as she had already booked her place in the $6 million end-of-season grand finale, next month's WTA Championships in Istanbul, which features the top eight women's players.
"I'm always very, very happy that I still can be one of the top seeds here," she told reporters in Beijing. "It's never easy here, so I am just really trying not to think about any pressure, especially that I made the qualifying already for Istanbul."
She added that she was "just going to try to play my best tennis here and trying to win it again".
Radwanska faces Switzerland's Stefanie Voegele in her opening game at the tournament on Monday.
The China Open will reach its climax on October 6.