The Federal Reserve would consider reopening its program to support the mortgage market if interest rates spiked or the economy showed new weakness, Federal Reserve Bank of New York President William C. Dudley said in two new interviews. The Fed is buying $1.25 trillion in mortgage-backed securities in its effort to prop up the economy but has said it will end those purchases March 31. In interviews with the Nightly Business Report and the Associated Press, Dudley said the time is right to end the program because the economy is growing and because expanding the purchases would make it harder for the Fed to unwind its support down the road.