The economy hasn't been growing nearly as quickly as the Federal Reserve thought it would. That alone probably isn't enough to shake its intention to start reducing bond purchases in September, but it can't be feeling as comfortable with that plan as it had been.

The Commerce Department reported Wednesday that gross domestic product rose at a 1.7% annual rate in the second quarter, a figure better than the 0.9% economists were looking for. But the number was clouded by caveats.