Fed Barkin: Longer-term borrowing costs rising because of increased economic optimism

Reserve Bank President Thomas Barkin said on Friday that longer-term borrowing costs are rising because of increased economic optimism and some expectations of rising inflation, 

Barkin also said the Fed won't be raising short-term interest rates until the economy meets clear benchmarks.

"I expect to start raising rates when we meet the conditions that we've talked about," Barkin said on CNBC.

"I don't have a sense that there's a timing, there's a year, there's a month, there's a quarter that I'm thinking about," he said.