Japan is stepping up its warnings over yen weakness as policymakers seek to prevent further depreciation from adding to import costs and inflation. Atsushi Mimura, Japan’s top currency diplomat, said Monday that markets should take seriously the message recently delivered by Tokyo and Washington, while declining to disclose whether Japan was preparing another currency intervention.

Tokyo Sends a Stronger Signal to Currency Markets

Mimura said Japan’s prime minister, finance minister and the United States had delivered a “very clear message” regarding the yen. He added that he would closely monitor whether markets continued to treat that message seriously.

His comments immediately affected foreign-exchange trading. The yen strengthened through the 157 level against the dollar and traded around 156.75 following the remarks, underscoring how sensitive the currency has become to signals from Japanese policymakers.

Intervention Remains Deliberately Unclear

Mimura declined to say whether Japan was prepared to intervene in the currency market again, either independently or in coordination with the United States. Instead, he said he had no comment on how Tokyo could act.

At the same time, he dismissed concerns that financial constraints could prevent Japan from intervening again. His comments therefore leave the precise policy response undefined while maintaining pressure on traders to account for the possibility of official action.

Why a Weak Yen Matters for Japan

Yen depreciation has become a policy concern partly because it raises the cost of imported goods, including energy. That issue has become more significant as elevated oil prices linked to the Middle East conflict increase Japan’s import bill.

The currency’s weakness has persisted despite the Bank of Japan moving its policy rate higher. According to Mimura, the broader direction of Japanese and U.S. monetary policy is important because the gap between their policy rates has been narrowing as a trend. However, the pace of that adjustment remains a key consideration for foreign-exchange markets.

The Rate Differential Remains a Major Constraint

Japan’s higher interest rates have not automatically translated into a stronger yen. The dollar continues to benefit from relatively high U.S. yields, meaning investors remain focused on how quickly the interest-rate gap between the two economies could narrow.

That creates a complicated backdrop for Tokyo. Policymakers can use communication to discourage excessive currency moves, while the underlying rate differential can continue to influence capital flows and demand for dollars. The yen’s reaction to Mimura’s comments therefore shows the immediate impact of policy signaling without resolving the broader monetary-policy divergence.

Japan and U.S. Coordinate on Currency Concerns

Japan and the United States have recently emphasized their shared concern over yen weakness. Japan’s Finance Minister Satsuki Katayama and U.S. Treasury Secretary Scott Bessent reaffirmed during Friday discussions that the yen’s undervaluation was an issue of concern.

Mimura has also described the broader relationship between Tokyo and Washington as extending beyond foreign exchange to economic security, critical minerals and global supply chains. He characterized the relationship as very strong and linked that cooperation to the countries’ previous coordinated currency intervention.

Fiscal Policy Adds Another Layer

Market participants have also debated whether Japan’s fiscal policy could contribute to yen weakness by encouraging expectations for stronger domestic demand and inflation. Mimura pushed back against the view that Japan’s fiscal stance had been criticized internationally as excessively expansionary.

He said he had not received criticism from G7, G20 or other overseas counterparts that Japan’s fiscal policy was too expansionary. That suggests Tokyo does not view fiscal policy as the primary explanation for the currency’s recent weakness, although markets continue to monitor the interaction between government spending, inflation and monetary policy.

What Could Matter Next for the Yen?

The next test for the yen will be whether Monday’s policy warning produces a lasting change in market positioning or only a temporary reaction. Further depreciation could increase attention on the possibility of official intervention, while a narrowing U.S.-Japan rate gap could provide a separate fundamental source of support.

For currency markets, the combination of Japanese policy signaling, U.S. interest rates, energy prices and inflation expectations will remain important. Tokyo has made its concern increasingly explicit, but the yen’s longer-term direction will also depend on whether monetary-policy differences between Japan and the United States continue to narrow.