The U.S. Treasury Department has issued a stark warning regarding the Japanese yen, stating that excessive volatility in the currency is undesirable and calling for the Bank of Japan to implement further interest rate hikes.

The department noted that yen weakness has persisted despite a narrowing in the interest rate differentials between the United States and Japan, suggesting that market forces alone are not stabilizing the exchange rate.

This intervention marks a significant escalation in Washington’s stance on the yen, moving beyond general observations to direct policy recommendations.

The Treasury’s comments underscore a growing frustration with the currency’s trajectory, which has remained under pressure even as the gap between U.S. and Japanese borrowing costs has begun to close.

By explicitly linking the yen’s performance to the need for BoJ action, the U.S. is signaling that it views the current monetary policy divergence as a source of global financial instability.

The warning comes amid a complex backdrop for the Japanese currency.