The Fed says it plans to keep its key short-term rate near zero at least until the unemployment rate drops below 6.5 percent — as long as expected inflation is tame. Unemployment is now 7.7 percent.

That plan adds detail to what the Fed had said before: that it expects to keep the rate low until at least mid-2015. For the first time, the Fed is making clear to investors and consumers that it will link its actions to specific economic targets.

In a statement Wednesday after its final policy meeting of the year, the Fed also said it will keep spending $85 billion a month on bond purchases to drive down long-term borrowing costs and stimulate economic growth.