By Makiko Yamazaki and Leika Kihara

TOKYO, Aug 3 (Reuters) – Japan is expected to announce on Monday that it took joint action with the U.S. to halt ‌the yen’s slide to 40-year lows and express its commitment to rare bilateral coordination ‌that it hopes could mark a turning point for the currency.

Finance Minister Satsuki Katayama will announce on Monday morning ​that Tokyo and Washington acted together in the currency market last week to arrest what they consider excessive yen declines, two Japanese government officials told Reuters over the weekend, with one saying the operation was “still ongoing.”

Her expected remarks to reporters follow what market sources say were rounds of ‌yen purchases by the Japanese and ⁠U.S. authorities, the first joint intervention in 15 years, seeking to support the battered currency.

Japan has been struggling to curb a relentless drop in ⁠the yen that pushes up import prices and stokes broader inflation, hitting households’ wallets and Prime Minister Sanae Takaichi’s public approval ratings.

Japan may have sold as much as $58.97 billion to buy yen when ​it ​intervened in New York markets on Thursday, Bank of ​Japan data indicated, followed by another ‌suspected foray into the market on Friday.

On Friday, the U.S. Treasury told a number of banks it too might intervene in the yen market, a source told Reuters, while Treasury Secretary Scott Bessent — who had said the yen “seems very undervalued” — had a handwritten “To Do” list at a cabinet meeting that said, “Buy Japanese Yen (JPY) $5-10 bil”, a Reuters photo showed.

In line with Bessent’s repeated ‌calls for higher Japanese interest rates, the Bank of ​Japan on Friday offered its most explicit signal to ​date of an early rate hike, ​even as it kept monetary policy steady.

In a sign of broader policy ‌coordination, South Korea stepped in to buy ​its won currency on Thursday.

The ​dollar ended Friday trading around 157.60 yen, having retreated from near 164 yen, the highest since 1986, which it hit earlier in the week.

Japan intervened in April and ​May, buying yen, causing only ‌a brief rebound. The BOJ’s June rate hike to a 31-year high of ​1% also gave the struggling currency little lasting boost.

(Reporting by Makiko Yamazaki and ​Leika Kihara in Tokyo; Editing by William Mallard)