WASHINGTON, March 25 (Reuters) - Any changes to current Federal Reserve policy will come “gradually and with great transparency” and only after the economy has more fully healed, Fed chair Jerome Powell said on Thursday. “As we make substantial further progress towards our goals we will gradually roll back,” the $120 billion monthly bond purchases the Fed currently makes, Powell said in an interview on National Public Radio’s Morning Edition. Rate increases would only be considered “when the economy is all but fully recovered.”