The Federal Open Market Committee could call it quits on QE3 after meetings Tuesday and Wednesday. The Fed has bought more than $4 trillion worth of Treasuries and Mortgage bonds in its extraordinary effort to stimulate the economy.

For six years, the Fed has used some form of the unconventional monetary policy known as quantitative easing. When that ends, the Fed still has its conventional tools.

“So the Fed still can influence short-term rates, thirty-day rates, overnight rates,” says Rutgers University’s Morris Davis, who was once an economist with the Federal Reserve Board. “It just has decided it will not try to influence longer term rates like the ten-year Treasury or mortgage-backed securities.”

But even if the Fed stops its bond buying program, it won’t stop buying bonds. Interest-rate strategist Ian Lyngen with CRT Capital Group says the Fed plans to replace all those securities it owns as they mature. He says the Fed wants to maintain the size of its balance sheet for now, with those trillions injected in the economy.

He describes the thinking like this:

“We’ve put that much more money into the system, and we’ve provided that much more stimulus. And as long as we’re not shrinking the size of our balance sheet, then we’re continuing to keep our foot on the pedal.”

We’re just not accelerating more.