Japan’s yen extended its recent decline, falling back to a level that could trigger a fresh round of intervention from government officials that has the potential to roil U.S. stocks during the traditional August lull. Japan’s Ministry of Finance has spent billions propping up the yen this year, including a record $53 billion in late July when it joined forces with the U.S. Treasury Department for the first time since 1998 to arrest the currency’s yearslong slide. Since then, however, the yen has given back around half of the gains it established over those two trading sessions in July, and was last trading at 159.17 against the U.S. dollar.