US and Japan Forge 'Currency Alliance' With Coordinated Intervention, Citi Says

Recent joint intervention in currency markets by the United States and Japan signals an informal “currency alliance” that connects foreign-exchange policy with the two nations' wider economic and national security relationship, according to Citi strategists.

A New Strategic Coordination

In a research note, Citi said the arrangement should not be seen as a formal monetary union, but rather as a new level of policy coordination. The analysis cited Japan’s Vice Finance Minister for International Affairs, Atsushi Mimura, who reportedly described the latest intervention as the culmination of this alliance. The move may also provide support for Japan’s $550 billion U.S. investment program.

Citi strategists noted that while the action is not a full implementation of the proposed “Mar-a-Lago accord” to reshape the international monetary system, it does incorporate elements of that framework. Specifically, the dollar-selling intervention was conducted through the Federal Reserve’s Foreign and International Monetary Authorities (FIMA) facility.

Washington's Rationale

According to Citi, the U.S. action reflects growing concern from Treasury Secretary Scott Bessent that prolonged weakness in the yen could recreate conditions similar to those preceding the Asian currency crisis of the late 1990s. President Donald Trump’s characterization of the intervention as a “signal of friendship” suggests high-level political support in Washington for the move.

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The intervention may also serve as a warning to Japanese Prime Minister Sanae Takaichi, whose reflationary policies could exert renewed downward pressure on the yen. Citi believes Washington's participation signals a desire for Tokyo to moderate its economic policy stance.

Market Implications and Historical Parallels

Citi drew a comparison to 1998, when the U.S. initially declined to participate in a coordinated intervention. The yen subsequently plunged before a market shock following the collapse of Long-Term Capital Management caused the USD/JPY to plummet from ¥147 to ¥108 within six months.

An unusual feature of the latest action was the U.S. selling euros to purchase yen. Citi views this as a temporary portfolio shift by the Treasury’s Exchange Stabilization Fund, moving assets from a historically expensive euro into an undervalued yen. The bank suggested Japan could take similar action if the EUR/JPY cross rate rises toward the ¥185 to ¥186 range, with the goal of pushing the pair below its recent low near ¥180.

Traders will now look to upcoming events for further policy clues, including the Jackson Hole symposium from August 27-29 and the G7 and G20 finance meetings scheduled for late August and early September.