The greatest risk to global portfolios from Japan's currency crisis could be the potential for disruption in the U.S. Treasury market as Japan intervenes to prop up the yen, deVere Group's Nigel Green says in a note. If Japanese authorities are forced into sustained intervention, they may have little choice but to liquidate substantial foreign reserves, including U.S. government bonds, potentially creating fresh pressure in the world's most important debt market, the CEO says. "Everyone's focused on whether Tokyo will intervene in the currency market," he says. "The more important question is how Japan pays for that intervention." In Asian trade, the yen dropped to 162.41 per dollar, its weakest in 40 years, LSEG data show. (emese.bartha@wsj.com)