A top Federal Reserve official said Thursday he's worried about the weakness of the U.S. economic recovery but doesn't think it will slip into another recession. William Dudley, president of the Federal Reserve Bank of New York, said in an interview with The Associated Press: 'I think we do have a sustainable economic recovery.' But he added: 'I'm less confident how strong that recovery will be.' The odds that the economy will fall back into recession 'are low, but not zero,' he said. To energize the recovery, the Fed has pledged to hold interest rates at record lows for an 'extended period,' which some analysts say means at least six months. Dudley said that with unemployment high and factories operating well below capacity, the Fed can be 'quite patient' before reversing course and raising rates. The New York Fed chief also left the door open to a possible extension of an emergency program aimed at driving down mortgage rates and bolstering the housing market. The Fed is on track to end its $1.25 trillion purchases of mortgage securities at the end of March. If the economy were to turn much weaker than expected or if mortgage rates were to sharply rise, it could prompt the Fed to extend the program, Dudley said. Dudley likened the situation to the Fed driving a car. 'If there's a sharp turn in the road,' the Fed will adjust course. 'Nothing is on automatic pilot,' he said. For now, Dudley doesn't think mortgage rates will jump when the program ends because the Fed has put investors on notice for months about the March 31 end date. Some worry that the Fed's record-low interest rates near zero could feed some new speculative bubble. The Fed has left rates at record lows for more than a year. Dudley said he doesn't see any new bubbles 'at this stage.' 'A lot of the improvement in asset prices is desirable,' reflecting the economic recovery, he said. On the Fed's unpopular bailout of insurance giant American International Group Inc., Dudley indicated the Fed didn't have the time or leverage to extract concessions from AIG's Wall Street trading partners, which ended up being paid in full by AIG. Federal Reserve Chairman Ben Bernanke's Senate battle last week to win confirmation for a second term hasn't hurt the Fed boss' effectiveness 'one iota,' Dudley said. But the spectacle does raise concerns about Congress trying to nibble at the Fed's independence, he said. The Fed must make decisions that might be unpopular but right for the economy without interference from Congress, Dudley said. 