Illustration: Xia Qing/GT

The yen has weakened in recent days, edging closer to the psychologically important 160 level against the US dollar. The decline comes despite the widely watched move by Washington to join Tokyo in supporting the currency. Less than two weeks after the US-Japan intervention, the yen has given up roughly half of its gains, raising fresh questions over the effectiveness of coordinated efforts to stabilize the exchange rate.

Japan and the US had previously confirmed coordinated foreign exchange intervention to prop up the yen after the currency tumbled to a nearly 40-year low. At the time, some observers saw the move as potentially stabilizing the yen in the short term, although its longer-term impact remained uncertain. 

However, the subsequent market reaction suggests that even the short-term effect may have been limited. After strengthening to about 155 per dollar in the days following the intervention from above 163, the yen had slipped back above 159 by Wednesday, less than two weeks later.

Questions have emerged over whether further support for the yen may soon be needed, and whether Washington would consider stepping in again. The previous intervention was seen by some observers as a test of market confidence: the unusual coordinated move had the potential to influence market expectations and discourage bets against the yen. But if market expectations remain largely unchanged, repeated interventions could deliver diminishing returns. The US may face a difficult trade-off. Another intervention could require greater resources and come at a higher cost, while refraining from further action could raise questions over the lasting impact of the previous effort.

Market commentary has added to the uncertainty. Axios published a report headlined "Yen's weakness shows market isn't done pushing," while some reports suggested that the impact of the US-Japan intervention was beginning to fade. Such narratives could weigh on sentiment toward the yen and reinforce market expectations that the currency's weakness may persist.

Washington's involvement in supporting the yen may reflect broader economic and policy considerations. These could include avoiding a scenario in which Japan sells US Treasury holdings to support the currency, as well as concerns that a weaker yen could give Japanese exporters a greater competitive advantage. These possible considerations suggest that the intervention alone does not fully address the underlying forces behind the yen's weakness. This may help explain why the market has so far been reluctant to view the move as a turning point for the currency.

Washington's decision to join the intervention may have reflected concerns, as some observers suggest, that the yen's prolonged weakness had begun to affect US interests. If markets remain unconvinced by the US-Japan intervention, one possible outcome is that Washington could push Japan to take more costly measures to support the yen. Such a scenario could instead create some strain between Washington and Tokyo.

Beyond short-term market dynamics, the yen's weakness also reflects deeper challenges facing the Japanese economy, making a sustained reversal difficult. The currency's prolonged weakness has been influenced by the interest rate gap between Japan and the US, while also reflecting longer-term concerns over the diminishing returns of Japan's traditional growth model.

This leaves Japan facing a delicate policy balance between supporting growth and stabilizing the currency. While lower interest rates could help boost economic activity, continued weakness in the yen may strengthen calls for Japan's central bank to consider further rate increases to narrow the interest rate gap with the US.

Japan's structural challenges mean that a sustained appreciation of the yen will not be easy to achieve. The question of whether to pursue stronger measures, even at the cost of some economic growth, has become more complicated as the US takes a role in the issue. Japan may face greater pressure to support the currency, even though doing so would be difficult and could carry broader economic costs.

The author is a reporter with the Global Times. bizopinion@globaltimes.com.cn