Substantial discussions on trade, including reform of the World Trade Organization, will likely take place at a summit of Group of 20 major economies next week in Osaka, a senior Japanese finance ministry official said.

Japan, which chairs this year's G20 gatherings, will take a neutral stance in the U.S.-China trade row and urge countries to resolve tensions with a multilateral framework, said Masatsugu Asakawa, vice finance minister for international affairs.

"With regard to differences (on trade) between the United States and China, Japan of course won't take sides. We will also not take any steps that go against WTO rules. Japan will continue to take a multilateral approach in promoting free trade," Asakawa told.

More "concrete" discussions on trade policy will take place at the G20 Osaka summit, he added.

Asakawa rebuffed the view the Bank of Japan's massive stimulus programme could provoke the ire of Trump. He also said the G20 shared an understanding that members would accept any exchange-rate moves driven by ultra-easy monetary policies as long as the measures are not directly aimed at manipulating currencies.