The US Treasury Secretary has delivered an unequivocal message to Japan's top monetary officials, urging an interest rate hike and strengthening market bets on a September move by the Bank of Japan.

According to recent reports, Treasury Secretary Bessent held talks with Japanese Finance Minister Katsunobu Kato and Bank of Japan Governor Kazuo Ueda on the sidelines of the G20 Finance Ministers and Central Bank Governors meeting in North Carolina, explicitly stating that Japan's next step should be raising rates. This marks a more direct tone than previous communications, intensifying speculation that the BOJ could tighten policy at its September 17-18 meeting.

Quoting US Treasury Under Secretary for International Affairs Erin Browne, Bessent emphasized during the discussions that Japan needs to clearly signal to markets that it is clearing the path for fiscal sustainability and progressive monetary tightening. Prior to this, Bessent had already told Reuters that he expected the BOJ to "do the right thing" on monetary policy and revealed plans to meet with Governor Ueda during the G20 gathering.

Rising Rate Hike Expectations and Doubts Over Intervention Effectiveness

Japan's Ministry of Finance foreign exchange intervention serves as a last-resort defense, yet July's experience has laid bare its constraints. The coordinated yen-buying operation briefly pushed the dollar-yen pair back toward 155, only for the exchange rate to approach the 160 threshold again just a month later. Markets keep reverting to the same logic: powerful carry trade dynamics, subdued volatility, and Japanese monetary policy still trailing the curve.

Last Friday, Japan's Ministry of Finance reported record intervention totaling 15.4 trillion yen (approximately $96.4 billion) over the past month. Washington has not disclosed its own yen purchase figures, though estimates suggest they were substantially smaller than Tokyo's.

When asked by CNBC about the yen's persistent weakness since the July 31 joint intervention, Bessent remarked: "I cannot influence the natural equilibrium exchange rate; what we can do is send signals. I possess information that markets don't have, and I trust that the Japanese government and central bank will take actions conducive to a stronger yen." He added, "I believe markets have now priced in the rate hike expectations."

Consistent Stance: Rate Hikes Preferred Over Intervention

Over the past year, Bessent has repeatedly signaled his preference for BOJ rate hikes to support the yen rather than repeated market interventions. His direct comments during the G20 meetings represent a continuation and reinforcement of this position.

Speaking to Reuters on Sunday, Bessent noted that recent yen movements have been "reasonably well contained," lacking the "disorderly" characteristics that previously triggered intervention, marking a slight softening in rhetoric. However, coupled with his explicit endorsement of rate hikes during bilateral talks, markets broadly interpret this as Washington wanting Japan's central bank to replace FX intervention with policy action to fundamentally stabilize the currency.

Overseas Assets and Capital Repatriation: The Real Determinants

The yen's true vulnerability lies in Japan's massive accumulation of overseas assets, not marginal shifts in policy rates. A substantial capital repatriation wave or near-term rebalancing by the Government Pension Investment Fund (GPIF) could meaningfully alter the yen's trajectory. Yet, neither scenario currently shows signs of materializing.

Meanwhile, waiting for Japan's real interest rates to catch up with global peers offers little short-term comfort. The potent combination of low volatility and the magnetic appeal of carry trades forms the structural underpinning of yen weakness — a dynamic unlikely to dissipate anytime soon.