From the article:

Japanese Finance Minister Satsuki Katayama will announce on Monday that Tokyo and Washington took joint action in the currency market to arrest the yen’s slide to 40-year lows, two Japanese government officials told Reuters.

Katayama is likely to stress the two countries’ determination to combat what they consider excessive yen declines, said the sources familiar with the matter, on condition of anonymity due to the sensitivity of the issue.

One source, asked if Katayama would announce “joint action”, said yes, adding, “The operation is still ongoing.”

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The expected announcement follows what market sources say were rounds of yen-buying in the market by the Japanese and U.S. authorities, the first joint intervention since 2011, seeking to boost the Japanese currency from its lowest levels against the dollar since 1986.

[...]

Tokyo’s initial intervention came hours before the BOJ decided on Friday to keep monetary policy steady while signalling a strong chance it would raise interest rates soon. A widening rate differential with the U.S., where the Federal Reserve has dramatically shifted to a more hawkish stance, has been a key factor in the dollar’s rise against the yen.

[...]

Critics have said Japan could face constraints to continued yen-buying intervention, as selling down its huge Treasury holdings to fund such action could trigger a selloff in U.S. debt and cause an unwelcome spike in U.S. yields.