By Howard Schneider and Ann Saphir WASHINGTON (Reuters) -The U.S. central bank could scale back the pace of its interest rate hikes “as soon as December,” Federal Reserve Chair Jerome Powell said on Wednesday, while warning that the fight against inflation was far from over and key questions remain unanswered, including how high rates will ultimately need to rise and for how long. “It makes sense to moderate the pace of our rate increases as we approach the level of restraint that will be sufficient to bring inflation down. The time for moderating the pace of rate increases may come as soon as…