Former Ambassador to China Uichiro Niwa has questioned Japan's Sept. 11 purchase of three of the Senkaku islets, which are administered by Tokyo but claimed by Beijing, suggesting the timing was less than ideal.

"Why rock the boat at such a time? I thought that while I was in China," Niwa, 73, said Thursday at the Japan National Press Club in Tokyo.

The remark apparently referred to Japan's acquisition of three of the five main islets in the Senkaku group from their private Saitama owner, just after Chinese President Hu Jintao had urged Prime Minister Yoshihiko Noda to refrain from taking the step.