James Bullard, President of the St. Louis Federal Reserve Bank, speaks during an interview with Reuters in Boston, Massachusetts August 2, 2013. REUTERS/Brian Snyder

LONDON (Reuters) - It will take at least five years for the U.S. central bank to trim its balance sheet to a conventional size that would give it room to undertake quantitative easing again in the future, St. Louis Federal Reserve President James Bullard said on Thursday.

“No matter how you cut it, you’re talking five years at a minimum probably to get to a kind of balance sheet size that is more conventional and will give us policy space if we wanted to do QE again the future,” Bullard told an event in London.