2015-06-20T214137Z_1544892382_GF10000134310_RTRMADP_3_USA-ELECTION-CLINTON
Hillary Clinton addresses the annual meeting of the U.S. Conference of Mayors in San Francisco, June 20, 2015. The American Federation of Teachers endorsed Clinton for the Democratic nomination Saturday. Reuters/Stephen Lam

Democratic presidential candidate Hillary Clinton said on Saturday the United States has to be "much smarter" about how it deals with Russian President Vladimir Putin.

"That's why we have to be much smarter in how we deal with Putin and how we deal with his ambitions," Clinton said at a campaign event. "He's not an easy man ... But I don't think there is any substitute other than constant engagement."

(Reporting by Amanda Becker; Writing by Eric Beech; Editing by Sandra Maler)