The Fed announced its action in a statement after a two-day policy meeting.
The central bank will continue a program called Operation Twist through year’s end.
Under the program, the Fed has been selling $400 billion in short-term Treasurys since September and buying longer-term Treasurys. It said it will extend the program through December using $267 billion in securities.
But extending Operation Twist might not provide much benefit. Long-term U.S. rates have already touched record lows. Businesses and consumers who aren’t borrowing now might not do so if rates slipped slightly more.