The yen has weakened back to 158.45 per dollar after the United States and Japan jointly intervened in the market with a combined total of around 87 billion dollars, marking their first coordinated yen-buying operation since 1998. The yen has surrendered nearly half of its earlier gains, retreating from its strongest level of 155.23 per dollar reached on Monday. Analysts at Oversea-Chinese Banking Corp. see a high likelihood of further intervention if the yen approaches the 160 level. Meanwhile, Bloomberg data suggests that authorities may have spent about 34 billion dollars on intervention on July 31 and another roughly 53 billion dollars the previous day, which if confirmed would be the largest single-day intervention on record. Japan's top currency policy official said authorities stand ready to respond to market moves in coordination with monetary policy.