HONG KONG, June 1 (Reuters) - Stock index provider MSCI is flexible on the timing of when it holds reviews on whether to include Chinese A shares in its indices and is not bound to an annual schedule, an official told reporters on Monday.

The decision on whether to include mainland Chinese shares in the indices is closely monitored by fund managers worldwide, since it could cause billions of dollars to flow into China's markets.

"We will stay as flexible as possible and are not rigidly bound to the year-to-year cycle," said Chin Ping Chia, head of research for Asia Pacific at MSCI at a media briefing in Hong Kong on Monday.

The index provider officially has a June-to-June schedule for reviewing which countries to include in its indices.

(Reporting By Michelle Price, writing by Lawrence White; Editing by Michael Perry)