It will take almost all of 2013 to see a material improvement in jobs growth in the United States, meaning the Fed should maintain its current aggressive pace of bond buying to stimulate growth for at least that period, Chicago Federal Reserve Bank President Charles Evans said Monday. The FOMC announced Sept. 13 that in addition to its maturity extension program, it will buy $40 billion in mortgage-backed securities a month -- and undertake additional asset buying if needed -- until it sees a significant improvement in the labor market, for a total of $85 billion in monthly asset purchases. It also pushed out its forward guidance -- how long its expects interest rates to remain close to zero -- to mid-2015 from late-2014. The maturity extension, or 'Operation Twist', expires at the end of the year, and Evans said in an interview on CNBC that the Fed must decide if $85 billion a month in asset purchases is enough in order to achieve "substantial improvement" in labor markets. "I frankly think its going to take almost a year in order to see the type of improvement in labor markets that I'm expecting -- just getting through the first half of next year with the headwinds that we are facing -- I think that it's probably later in 2013 that we would get there," Evans said. "So in my opinion we'd continue with those asset purchases until we see payroll employment (growth) more like 200,000 or 250,000," he added, recommending that the Fed continue buying $85 billion in longer date securities a month all of 2013. "If you go from a period where you've got $85 billion dollars (a month) being added to long duration assets to one where it's only $40 billion, well that's a step down in what you are delivering," Evans said. As for whether the Fed will persist with the mix of Treasury and mortgage-backed securities, Evans said the central bank will look at the state of financial markets and their ability to absorb the Fed's actions. "We've looked at it, it shouldn't be a problem," Evans said. Another question will be whether the economy is improving and so the program should be tailored and reduced a little bit, "or expanded if we are not getting quick enough improvement," he said. Evans said the effect of the Fed's actions should be mean economic growth between 2.5% to 2.75% next year, while the unemployment rate should drop to the 7% range by the end of 2014.