Naomi Osaka climbed two places to world No. 4 in the latest WTA rankings released Monday, equaling the highest-ever standing by a Japanese player.

The 20-year-old -- who was born in Osaka and raised in the United States by her Japanese mother and Haitian father -- started the year as No. 68 but soared up the rankings with titles at Indian Wells in March and the U.S. Open last month.

"I am really excited about it," Osaka told reporters at the Hong Kong Open tournament from which she has withdrawn due to back injuries. "I know that Kimiko (Date) was No. 4 too, so I think that makes us tie or something. But, for me, the year's not done yet. I want to keep playing and I want to see how far I can go."

She finished runner-up at the Toray Pan Pacific Open in Tokyo late last month and reached the semifinals of the China Open which concluded Sunday.

"I injured (my back) in the beginning in Beijing, doing something that not so athletic. I was more worried I wouldn't be able to play Beijing. And then it got better slowly, and then it got worse again. So I think just having time off for me is more important because I haven't really rested since the U.S. Open," she said.

"Right now I am just doing treatment and stuff and I was told in Beijing to rest for a couple of days, so I think I'll just see how it goes after a couple of days. For me, definitely I don't want to stop at just one grand slam, of course I want to win more, but right now it's not the Australian Open, it's, like, Singapore, so I have to look forward to that," she said.

The top three players remain unchanged, with Romania's Simona Halep holding onto the No. 1 position, followed by Caroline Wozniacki of Denmark and Angelique Kerber of Germany.

Two other Japanese players have previously reached world No. 4 -- Kimiko Date, in 1995, and Kei Nishikori, who most recently held the rank in March last year.

Osaka earlier this month qualified for the season-ending WTA Finals Singapore for the first time in her career.

The world's top eight players will compete in the Oct. 21-28 round-robin tournament with a $7 million total prize purse on the line.