The Bank of Japan is laying the groundwork for deepening negative interest rates, analysts polled by Reuters said, with two-thirds of respondents expecting the central bank to loosen monetary policy this month.

Risks to the global economy have risen from the protracted U.S.-China trade war and Brexit, among other factors, and Japan's central bank is not alone in having to consider launching more stimulus to avert a sharp slowdown.

At its rate review last month, the BOJ said it would take a more thorough look at whether heightening overseas risks could derail Japan's fragile economic recovery.