BEIJING (Reuters) - U.S. Treasury Secretary Jack Lew said the optimal window to make progress on a U.S.-China bilateral investment treaty (BIT) is before the G20 leaders meeting in September.

The comment was made late on Tuesday at the end of high-level strategic talks between the U.S. and China in Beijing.

(Reporting by David Lawder; Writing by Sue-Lin Wong; Editing by Will Waterman)