SAO PAULO (AFP) - Three-time French Open champion Gustavo Kuerten said that he is undergoing new medical tests to decide if he needs more surgery on a recurring hip injury.

Kuerten underwent surgery on the same hip in February 2002 but has since struggled to regain the form which took him to the world number one spot as well as his three Roland Garros titles.

"My lack of physical form has been an obstacle, but mentally I feel good," said 28-year-old Kuerten.

"The idea of surgery has surfaced because I worked enough this year and I didn't get the results I'd hoped for."

The world 23rd-ranked Brazilian lost to Kristian Pless of Denmark in the first round of the US Open earlier this month.

But Kuerten said that although he will undergo medical tests in the United States, he will need to be assured that surgery will bring results.

"I'll play a little so that (the doctors) can see what my limitations are. In order to arrive at surgery I must feel good in my head," he added.