WASHINGTON (AP) — Just as Ben Bernanke prepares to turn the chairmanship of the Federal Reserve over to Janet Yellen, global markets are on edge over the prospect that she’ll extend a policy he began: a steady pullback in the Fed’s extraordinary economic stimulus.

Managing a slowdown in the Fed’s bond purchases without roiling markets will pose a tough early test for Yellen, who succeeds Bernanke as Fed chair next week. The Fed’s bond purchases have been intended to keep long-term loan rates low to spur spending and economic growth.