September 23 -- A day after Bill Gross said central-bank support limits the downside for long-term government debt, former Federal Reserve Chairman Alan Greenspan called the bull market in Treasuries unsustainable. The yield on the U.S. 10-year note fell to the lowest level in two weeks even as Greenspan warned it may rise in the long run to as much as 5 percent. On Wednesday, the Fed lowered projections for the path of interest rates, while the Bank of Japan shifted the focus of its stimulus to controlling bond yields. The actions prompted Gross, manager of the $1.54 billion Janus Global Unconstrained Bond Fund, to say he favors longer-dated sovereign debt. Bank of New York Mellon Chief Currency Strategist Simon Derrick discusses with Bloomberg's Francine Lacqua on "The Pulse."