U.S. stock index futures turned slightly positive Wednesday after Fed Chairman Ben Bernanke reiterated the central bank's plan to start paring back its bond-purchase program later this year, but said that could change if the economic outlook shifted.
"Our asset purchases depend on economic and financial developments, but they are by no means on a preset course," according to Bernanke's prepared remarks to the U.S. House of Representatives Financial Services Committee.
Bernanke said the pace of asset purchases could be reduced "somewhat more quickly" if economic conditions were to improve faster than expected. On the other hand, the current $85 billion monthly pace "could be maintained for longer" if the labor market outlook darkened, or inflation did not look like it was rising back toward the Fed's 2 percent goal.
Bernanke will deliver his full testimony at 10 am ET, followed by a Q&A session from lawmakers. (CNBC.com will stream the event live.)