"Libra’s a new thing; we are looking at it very carefully," Powell said in response to an audience question after a talk at the Council on Foreign Relations in New York. "Given the possible scale of it, I think that our expectations -- from a consumer protection standpoint, from a regulatory standpoint -- are going to be very, very high."

Facebook said last week it wanted to expand into payments and launch its own coin, Libra, by next year.

"Authority for overseeing Libra is going to be in a number of places, but I think that the big picture is we are going to be looking really carefully at it," said Powell, whose cautious remarks echoed those of other financial regulators around the world about the possible new currency.

(Reporting by Ann Saphir; Editing by Chizu Nomiyama; Editing by James Dalgleish)