A rare joint intervention by the US and Japan highlights growing policy coordination as both countries seek to address yen weakness and its broader economic and security implications
The United States and Japan have taken the unusual step of coordinating their efforts to influence the Japanese yen, signaling a new phase of policy alignment that extends beyond traditional economic cooperation. According to Citi strategists, this informal "currency alliance" reflects a shared concern over the yen's persistent weakness and its potential to disrupt both financial markets and the broader US-Japan relationship.
Japan's Vice Finance Minister for International Affairs, Atsushi Mimura, described the latest intervention as the culmination of ongoing collaboration between the two countries. While this arrangement does not amount to a formal monetary union, Citi analysts emphasize that it represents a significant step in aligning foreign-exchange policy with wider economic and national-security interests. The policy coordination may also support Japan's substantial $550 billion investment program in the United States, further intertwining the two economies.
Policy Coordination and Market Impact
Citi's research suggests that the intervention should not be confused with a comprehensive overhaul of the international monetary system, such as the proposed "Mar-a-Lago accord." Instead, the current approach focuses on targeted measures, including dollar-selling operations through the Federal Reserve's Foreign and International Monetary Authorities (FIMA) facility. This mechanism allows the US to provide liquidity in foreign currencies, and its use in the recent intervention highlights Washington's willingness to act when yen depreciation threatens financial stability.
Treasury Secretary Scott Bessent is reportedly concerned that a prolonged period of yen weakness could recreate the conditions that preceded the Asian currency crisis of the late 1990s. In that period, unchecked declines in the yen contributed to regional instability and sharp market corrections. The US government's support for the intervention, described by President Donald Trump as a "signal of friendship," underscores the political dimension of the move. At the same time, the action may serve as a warning to Japanese Prime Minister Sanae Takaichi, whose reflationary policies could put renewed downward pressure on the yen. Citi believes Washington is encouraging Tokyo to moderate its stance to avoid further destabilization.
Historical Parallels and Unusual Moves
The current intervention stands in contrast to the US response in 1998, when American authorities initially declined to participate in coordinated action as the yen weakened. Following the collapse of Long-Term Capital Management, the USD/JPY exchange rate fell sharply from ¥147 to ¥108 within six months, illustrating the risks of inaction during periods of market stress. This time, the US has taken a more proactive role, including an unusual step of selling euros to buy yen. Citi interprets this as a temporary shift by the Treasury's Exchange Stabilization Fund, moving from a historically expensive euro into an undervalued yen. Should the EUR/JPY rate approach ¥185 to ¥186, Japan may consider similar intervention, though European authorities are likely to tolerate only limited euro selling.
Recent market data shows that the USD/JPY pair remains the primary focus for intervention, with authorities aiming to prevent excessive volatility. Citi notes that intervention could also target the EUR/JPY rate, seeking to push it below its recent low near ¥180, at least temporarily. The effectiveness and duration of these interventions remain uncertain, as market participants weigh the credibility and resolve of policymakers.
Key Figures and Upcoming Events
In the latest intervention, the US and Japan acted together to counter yen depreciation, with the USD/JPY exchange rate having previously tested multi-decade highs. For context, the yen's weakness has been a persistent theme, with the currency losing ground against the US dollar throughout much of the past year. The coordinated action follows a period in which the US dollar also experienced notable shifts, as seen when the Treasury Department expanded buybacks of long-term bonds, a move that contributed to a weaker dollar and shifting currency dynamics across Asia. For more on these recent developments, see this analysis of how Treasury buybacks have affected the US dollar's position.
Looking ahead, markets are expected to monitor the Jackson Hole symposium from August 27 to 29, followed by G7 and G20 finance meetings in Asheville on August 31 and September 1, for further signals on currency policy and potential intervention strategies.
Understanding Currency Alliances
Unlike formal monetary unions, which involve shared currencies and unified central-bank policies, informal currency alliances are based on coordinated but independent actions by sovereign governments. These arrangements allow countries to address shared risks-such as excessive currency volatility or destabilizing capital flows-without surrendering control over domestic monetary policy. The effectiveness of such alliances depends on the credibility of the participants, the scale of intervention, and the willingness of other major economies to tolerate or support coordinated action. In the case of the US and Japan, the current approach reflects both economic pragmatism and a recognition of the broader strategic relationship between the two countries.
