Business confidence at big manufacturers in Japan likely worsened to an almost three-year low in the April-June quarter, as the U.S.-China trade war and weakening global demand hurt the export-reliant economy, a Reuters' poll found Friday.

A deterioration in corporate sentiment will add to the Bank of Japan's concerns about slowing economic growth, after its governor signaled readiness to ramp up stimulus as global risks cloud the outlook.

The Bank of Japan's quarterly tankan business sentiment survey is expected to show the headline index for big manufacturers' confidence slipped to plus nine in June from plus 12 three months earlier, the poll of 16 economists showed.