Here's a look at the various uncertainties the central bank faces:
TO TAPER OR NOT
Though hiring and economic growth in the United States remain soft, the Fed is widely expected this week to slow the pace of its bond purchases. Its purchases of Treasury and mortgage bonds have been designed to keep long-term loan rates low to get people to borrow and spend and invest in the stock market.
Most economists expect the Fed's initial move to be small — a reduction in monthly purchases from $85 billion to $75 billion.
One reason: The Fed for months has been preparing markets for such a move. Fed officials wouldn't likely want to raise further uncertainty by failing to meet the very expectations they had raised.
Another factor: Some Fed officials don't think the bond purchases are doing much good anymore. And they feel that by continuing to flood the financial system with cash, the Fed might be raising the risks of high inflation or dangerous bubbles in assets like stocks or real estate.
Some had once expected a sharper first reduction in the Fed's purchases of around $20 billion a month. But that was before the government said that job growth was only modest in August and that employers added many fewer jobs in June and July than previously thought.
Investors' response to a pullback in purchases is expected to be mild if the Fed announces a reduction of only around $10 billion a month. That's especially true if it balances its action by underscoring its commitment to keep short-term interest rates low well into the future.
The Fed has kept its benchmark for short-term rates at a record low near zero since December 2008. And it has said it expects to keep it there at least until the unemployment rate falls to 6.5 percent — as long as the inflation outlook remains mild.
The unemployment rate is now 7.3 percent. Many economists do not expect it to reach 6.5 percent until late 2014 or early 2015.
Even then, Bernanke has said the Fed might decide to keep its short-term rate at a record low, especially if unemployment has dropped because more people have stopped looking for work. The government doesn't count people as unemployed once they stop looking for a job.