Japan is anticipated to declare on Monday that it has coordinated with the United States to curb the yen's slide to four-decade lows, signaling a rare bilateral policy alignment that Tokyo hopes will serve as a turning point for the currency.

Two Japanese government officials revealed over the weekend that Finance Minister Satsuki Katayama will announce on Monday morning that Tokyo and Washington jointly intervened in foreign exchange markets last week to halt what both sides consider excessive yen depreciation. One official described the intervention operations as "ongoing."

According to market sources, Katayama is set to address the media after multiple rounds of yen buying by Japanese and U.S. authorities. This marks the first joint currency intervention by the two nations in 15 years, aimed at propping up the persistently weakened yen, which has been on a unilateral downward spiral that has left Japan with few options.

The yen's decline has driven up import costs, exacerbated broad inflation, and increased the financial burden on households, while also dragging down support for Prime Minister Sanae Takaichi's cabinet. Bank of Japan data suggests that Tokyo may have deployed up to $58.97 billion to buy yen during intervention in New York markets on Thursday, with suspected further action on Friday.

Sources said the U.S. Treasury Department informed multiple banks on Friday that Washington might also step into the yen market. A Reuters photograph showed Treasury Secretary Scott Bessent with a handwritten to-do list on his desk during a cabinet meeting, which included "Buy yen (JPY) $5-10 billion." Bessent has previously stated that the yen is "significantly undervalued."

Bessent has repeatedly called on Japan to raise interest rates, a sentiment echoed by the Bank of Japan on Friday. Although the central bank kept monetary policy unchanged, it issued its clearest signal yet that it may accelerate the pace of rate hikes. The policy coordination has broadened further, with South Korea also entering the market on Thursday to buy the won.

At Friday's close, the dollar-yen exchange rate stood at around 157.60, down from near 164 earlier in the week—a level not seen since 1986. Japan intervened to buy yen in April and May, but those moves only produced temporary rebounds. A June rate hike by the Bank of Japan to 1%, a 31-year high, also failed to provide lasting support for the struggling yen.