The dollar-yen exchange rate touched above 160 again, putting the Japanese government on high alert. Japanese Finance Minister Satsuki Katayama said on Friday that recent currency markets have shown clear one-way and rapid moves, and that the government will take appropriate measures while continuing to communicate closely with the US Treasury.

Markets interpreted the comments as a sign that Tokyo's tolerance for yen weakness approaching a sensitive zone is fading. Adjustments to Federal Reserve rate expectations and a stronger dollar pushed the dollar-yen rate briefly to 160.03, its first move above 160 since early September. Yen weakness has heightened concerns about imported inflation and brought greater focus on policy coordination between the Bank of Japan and the government.

Japan's top currency official, Atsushi Mimura, had previously warned that it was premature for markets to forget the foreign exchange interventions carried out this summer. His remarks revived traders' caution about official market entry. From late July to early August, Japan intervened in the currency market for three consecutive trading days, when the yen approached 164 against the dollar, its weakest level in about 40 years. The Japanese government spent a cumulative 15.4 trillion yen, or about 96.47 billion dollars, in an intervention of record scale.

Meanwhile, the latest disclosure from the United States further indicated that the summer defense of the yen was not a solo effort by Tokyo. The Federal Reserve Bank of New York's quarterly foreign exchange market operations report said that on July 31 the US bought 79.4 billion yen in the spot market through the Exchange Stabilization Fund while selling euros. It was the first time since 1998 that the US had bought yen as part of a currency intervention, suggesting that Washington and Tokyo acted in coordination to support the yen.

With the yen again approaching 160, market attention has turned to two issues: whether the Japanese government will move from verbal warnings to actual intervention, and whether the United States will maintain the coordinated stance it took over the summer. For traders, the intensity, pace and transatlantic coordination of official intervention may become key variables shaping the yen's short-term direction.