Japanese yen slipped further against the US dollar on Wednesday, approaching the key 160 level and prompting investors to watch closely for any renewed government intervention.

At the New York close, the yen traded 0.1% lower at 159.43 against the greenback. The currency has declined over 1% this month, erasing part of the gains spurred by a recent joint intervention from the US and Japanese authorities.

As the yen neared a 40-year low near 164 at a critical juncture, the two governments coordinated to buy the currency. However, the limitations of such actions remain evident; the interest rate differential favoring the US dollar has caused the yen to give back a significant portion of its rebound, bringing it back near the key 160 threshold.

Nathan Thooft from Manulife Investment Management said, "It's too early to say the intervention threat has disappeared."

"The Japanese authorities have shown a willingness to act, including in coordination with the US Treasury, and levels near or above the previous intervention zone could make traders cautious," he added. "We are certainly still closely monitoring for intervention."

Japan's benchmark interest rate stands at 1%, while the Federal Reserve's target range is between 3.5% and 3.75%. Traders see a roughly 60% probability of a rate hike by the Bank of Japan in September, and a move in October is fully priced in. For the Fed, traders anticipate a possible rate cut before December.

"After the coordinated intervention with the US, confidence in Japan's commitment to defending the yen has increased," said Shusuke Yamada, a strategist at Bank of America. "However, the dollar-yen rebound without any intervention over the past week suggests that credibility appears to have faded."

Traders will focus on Japan's July producer price index data due on Thursday. Economists forecast an annualized growth rate of 7.4%, surpassing the 2023 high set in June.