Why is US buying Yen? Scott Bessent vows treasury ‘will not hesitate’ again | Explained

For the first time in three decades, the United States has reached into a foreign currency market to defend an ally's money, and the story behind that decision reveals as much about anxieties in Washington as a crisis unfolding in Tokyo.

What sparked the yen intervention?

The clearest early signal came not from a statement but a photograph. At a cabinet meeting at Camp David on Friday, a Reuters photographer caught Treasury Secretary Scott Bessent's notepad over his shoulder. Under the underlined heading "To Do" sat one instruction: “Buy Japanese Yen (JPY) $5-10 bil.”

President Donald Trump later confirmed the operation himself, framing it as an act of friendship rather than policy. "Japan's been very good to us, with the exception, of course, of Pearl Harbor," he said on Sunday.

Aboard Air Force One, President Trump added: "They have a weakening yen, and they wanted a little bit of help. And we're always there for Japan," calling the move "good for the world economy".

Why is the yen falling?

Japan imports almost all of its energy and much of its food, so a weaker yen makes both markedly costlier for households. That pressure has intensified this year as the war between the US and Iran disrupted oil and gas flows from West Asia, forcing Tokyo to spend heavily on fuel subsidies.

Beneath that sits a deeper problem. The Bank of Japan has held rates extraordinarily low since the deflationary 1990s, making the yen structurally unattractive to global investors. Public debt now exceeds 200% of GDP, the highest in the G20. The yen slid to 163.73 per dollar last Thursday, its weakest in roughly four decades, before recovering to 157.57 by Friday.

What's really driving Washington's involvement?

To fund its own yen purchases, Japan has been selling large volumes of US government bonds, and since Japan is among the largest foreign holders of treasuries, that selling can push up US borrowing costs. Yields on the 10-year Treasury have climbed almost 57 basis points since the start of the year.

Traders were also surprised to learn that the Federal Reserve Bank of New York sold euros, not dollars, to fund the purchases, a departure from past practice, the Financial Times reported.

Scott Bessent confirmed further action was likely, writing on X that the Treasury "will not hesitate to participate in further joint intervention," and that Washington "strongly support[s] Japan's decisive market and monetary steps to correct the substantial undervaluation of the yen."

Japan's finance minister, Satsuki Katayama, said the action "countered excessive volatility and disorderly movements in the Japanese yen in recent months."

How is this squeezing Japan Prime Minister Takaichi?

Prime Minister Sanae Takaichi says she spends nearly every waking hour on Japan's recovery, yet her poll numbers have slipped under rising import costs, the energy shock and a weakening currency.

In April, PM Takaichi cut sales tax on food and pledged hundreds of billions in fresh investment, the centrepiece of her pro-growth agenda.

That ambition carries risk. With debt at record highs, observers warn of a possible "Liz Truss-style shock," and the resulting uncertainty is itself seen as dragging the yen lower.

Takaichi's government has also approved Japan's largest military buildup since the Second World War, pledging to double defence spending to 2 percent of GDP within five years, a move welcomed in Washington even as critics call it a break from postwar pacifism.

Has US done this before?

Last October, Washington bought billions of Argentinian pesos ahead of a critical election for President Javier Milei, an ideological ally of Trump.

Scott Bessent said the purchase protected Argentina's "reform agenda," an austerity drive some called "shock therapy".

Will the intervention actually work?

The Bank of Japan intervened alone in late April, but those gains faded quickly. This time, Barclays believes the effect could last longer given the coordinated, historic nature of the operation, though it cautioned: “Even if the JPY were to strengthen further in the near term, we continue to believe that longer-term downward pressures remain in place.”