BEIJING — China grudgingly congratulated Japan on Monday on its successful bid to host the 2020 Olympics in Tokyo, after the government had initially refused to offer any praise over the supposedly non-political event.

Ties between the world's second- and third-largest economies have been shadowed for years by what Beijing says has been Tokyo's refusal to properly atone for wartime atrocities committed by Japanese soldiers in China between 1931 and 1945.

More recently, relations have been troubled by a sovereignty row over tiny, uninhabited islands in the East China Sea known as the Senkaku in Japan and the Diaoyu in China.

"We have noted the decision by the International Olympic Committee," Chinese Foreign Ministry spokesman Hong Lei told a daily news briefing.

Asked specifically whether China had offered congratulations, Hong said such a question should be directed to the Chinese Olympic Committee.

In a statement posted on the ministry's website after the news conference had ended, Hong said that the Chinese Olympic Committee had in fact expressed its congratulations. It did not elaborate.

Hong told reporters that China valued its relations with Japan, but it was up to Japan to stop its provocations over the disputed islands and correctly face its wartime past.

"We have said many times that we pay great attention to relations with Japan," he said. "At the same time we ask Japan to earnestly face up to history and facts."

China hosted a highly successful summer Olympics in Beijing in 2008, and Hong said this was an experience China could share with Japan, as he stuck a slightly more conciliatory note.

"China and Japan are important members of the International Olympic Committee community. We are willing to share the experience of hosting the Olympics with Japan," he added.