Japan spent 15.4 trillion yen ($96 billion) to boost the yen between late July and late August, the finance ministry said Friday, the largest monthly intervention on record.
The July intervention was the first time since 2011 when the United States and Japan -- and other G7 members -- sold yen to stop it rising after a huge earthquake.
The last time Washington and Tokyo bought yen was 1998.
Experts say the Trump administration also acted to reduce the US trade deficit -- a weak yen helps Japanese exporters -- and to help Japan invest $550 billion in the United States as promised under a 2025 trade deal.
While good for its big exporters like Sony and Toyota, a weak yen inflates import costs for resource-poor Japan, especially oil just as the Middle East war strangles supplies from the Gulf.
