Bank of Japan Governor Haruhiko Kuroda said the central bank will "certainly" debate heightening overseas risks at a rate review this week, underscoring concerns among policymakers about the economic fallout of a U.S.-China trade war.

"As for recent overseas economic developments, there are strong downside risks regarding the Sino-U.S. trade friction and China's economy," Kuroda told parliament.

"We'll certainly debate such overseas developments" at the upcoming rate review, he said, but added that the BOJ is already keeping monetary policy ultra-loose.

"The BOJ will guide monetary policy appropriately taking into account the impact overseas economic changes could have on Japan's economic outlook and the momentum for achieving our inflation target," Kuroda said.