The US-Japan yen intervention announced on Monday marks the first coordinated effort to buy the currency since 1998, and analysts are already warning it could destabilise one of the most heavily used trades in global finance.
Japan’s Finance Ministry confirmed it conducted yen-buying operations alongside the US Treasury on Friday to counter what it called ‘excessive volatility and disorderly movements in the Japanese yen in recent months,’ according to CNBC. The ministry vowed it ‘will not hesitate to conduct further coordinated interventions in the future.’
Treasury Secretary Scott Bessent confirmed the joint action, saying ‘Friday’s coordinated foreign exchange actions countered disorderly yen movements,’ according to the Council on Foreign Relations. He added that intervention can send a market signal but that Japan also needs to deliver policies that support the currency.
What the US-Japan Yen Intervention Actually Cost
The scale of the operation is coming into focus. Reuters reported that central bank data suggested Japan may have spent as much as $36.58 billion buying yen on Friday alone. Goldman Sachs estimated the total yen-buying across 30–31 July probably reached up to $85 billion, with potentially more deployed on 3 August given elevated volumes, according to a Goldman Sachs Exchanges podcast transcript.
A photograph taken at 11:33 a.m. US East Coast time on 31 July showed a notepad in front of Treasury Secretary Bessent during a Camp David cabinet meeting that read ‘To Do Buy Japanese Yen $5–10 bil.’, according to Nikkei Asia citing Reuters. The Federal Reserve Bank of New York executed the euro sales on behalf of the US Treasury through Goldman Sachs and Morgan Stanley, Nikkei Asia added.
The US has approximately €26 billion readily available across its System Open Market Account and the Exchange Stabilisation Fund, according to Reuters. The euro fell more than 4% against the yen, dropping from as high as 187.4 yen on Thursday to briefly below 180 on Monday. Barclays analysts told Reuters the choice to sell euros ‘avoids signaling a desire for broad-based dollar weakness, keeping the operation a yen-only affair.’
Goldman Sachs analysts noted in a separate note that the euro/yen rate of 187.50 appeared to be a key trigger level, as it had also prompted the April–May 2026 interventions when it was reached again in late July.
The yen surged more than 1% to 155.20 per dollar after the announcement, its strongest level since early May, having hit a 40-year low near 164 the prior month, Reuters reported. Finance Minister Katayama confirmed the joint operation was taken in accordance with a Japan-US Finance Ministers’ Joint Statement issued in September of the prior year, according to NHK World.
Context matters here. Japan had already spent a record 11.7 trillion yen (approximately $72.52 billion) on yen-buying interventions in April–May 2026, and raised interest rates in June 2026 to 1%, their highest level in 31 years, yet the currency’s weakness persisted, according to Reuters. The 1998 intervention was the last time the two countries acted jointly to support the yen, prompted then by a wave of Japanese bank failures, NHK World noted.
Carry Trade at Risk, Analysts Warn
The mechanics of the intervention are feeding concern about the yen carry trade, in which investors borrow yen at low rates and convert the proceeds into dollars to invest in higher-yielding assets such as US stocks and bonds.
Goldman Sachs analysts wrote that the fact the US sold euros rather than dollars suggests Washington does not want to weaken the greenback. ‘Further yen weakness or continued USD-selling/JPY-buying interventions by Japanese authorities, is not welcomed from the US perspective,’ the bank said. ‘Compared to a solo intervention by a country aimed at defending its currency (or curbing currency appreciation), a coordinated intervention sends a stronger message to the foreign exchange market,’ it added.
Robin Brooks, a senior fellow at The Brookings Institution, said the US move could reflect concern about rising yields. Japan’s Treasury sales to fund its own yen purchases can push US yields higher, and Brooks said the market would now be wondering if that dynamic was the overarching concern. The sale of euros added to uncertainty, he said, and could prove ‘counterproductive.’
Torsten Sløk, chief economist at Apollo, argued the yen carry trade had already started breaking down in April 2025, around the time of President Trump’s ‘Liberation Day’ tariff announcements. ‘The bottom line is that the yen carry trade has broken down, and the yen is no longer a rates story. Until volatility subsides, it will trade on Japan’s fiscal outlook rather than the interest rate gap,’ Sløk said.
Gus Garrow, a senior manager at StoneX, pointed to the Nasdaq 100 sell-off that accompanied the carry trade’s last meaningful unwind. ‘When the Japanese yen strengthens and the trade turns against its holders, investors are forced to raise cash quickly, and richly valued technology names are among the easiest positions to sell,’ Garrow said. ‘As a result, a currency move that begins in Tokyo can surface hours later as a deleveraging wave across US equities,’ he added.
Macquarie’s global FX and rates strategist Thierry Wizman pointed to the 1998 precedent: ‘The lesson of 1998 is that coordinated intervention in the USD/JPY to bring the pair lower can succeed, but it needs the extra catalyst of a large unwinding of JPY-funded carry trades to create a big move lower. The tinder is there in 2026.’ He flagged Bank of Japan policy tightening, falling oil prices, or a shift in Japan’s fiscal goals as potential catalysts, but added: ‘We still await those things.’
Meanwhile, the benchmark 10-year US Treasury yield stood at about 4.68% on Monday, above the 4.5% threshold closely watched by equity investors, while the 30-year yield hovered around 5.2%, close to its highest level since the Great Financial Crisis. In the intervention’s aftermath, Japan’s finance minister said future dollar-selling would be financed through the Federal Reserve’s FIMA repurchase agreement facility to avoid further Treasury sales, and Bessent publicly called for expansion of that facility, according to OMFIF. Whether the FIMA route becomes the new template, or whether the carry trade unwinds before policymakers can orderly manage the transition, will determine how this plays out for US equities in the weeks ahead.