Federal Reserve Vice Chairman Stanley Fischer in a speech in Colorado

Fischer took a somewhat hawkish tone in a speech in Aspen, Colorado but probably not enough to support the dollar when the market re-opens.

"Looking ahead, I expect GDP growth to pick up in coming quarters, as investment recovers from a surprisingly weak patch and the drag from past dollar appreciation diminishes," he said.

He didn't directly address the outlook for the Fed funds rate or monetary policy but said "we are close to our targets."

Fischer was constructive about the "resilient" employment market but called growth "mediocre at best" in a sign that he probably won't support at September hike.

He also continued the recent Fed trend of lamenting sort productivity.

"A 1.25 percentage point slowdown in productivity growth is a massive change, one that, if it were to persist, would have wide-ranging consequences for employment, wage growth, and economic policy more broadly," he said.

The next Fed decision is Sept 21 but Yellen is expected to deliver an important speech this week (Aug 26) in Jackson Hole, Wyoming.