Federal Reserve Bank of Boston President Eric Rosengren said on Friday the U.S. central bank may need the power to buy a broader array of bonds to provide stimulus given the sharp and historic decline in Treasurys yields amid the coronavirus outbreak.

He said the declines in U.S. government debt, most notably in the 10-year note, means that if the Fed runs out of room to lower rates, it also faces a very strong chance that Treasury bond buying—which featured prominently in the financial crisis and its aftermath as a stimulus...