US Education Secretary Arne Duncan defended in coming Chancellor Cathie Black yesterday, saying her lack of educational credentials won’t be an im pediment to running the city’s enormous school system.

“She, like anyone else, has a learning curve,” said Duncan, during a visit to a GED program in Midtown with Mayor Bloomberg.

“She’s smart; she’s committed; she’s going to have a great team . . . I think she has the potential to be a fantastic leader.”

Duncan also pledged to “do whatever I can in being supportive of her.”