The Federal Reserve is expected to leave interest rates unchanged at the end of a two-day policy meeting on Wednesday, but also indicate that a reduction in borrowing costs could come as soon as September. Contracts tied to the U.S. central bank's policy rate show investors are convinced a rate cut will happen at the Sept. 17-18 meeting, with the only disagreement over whether the Fed will begin easing policy with a quarter-percentage-point reduction, as most expect, or a more aggressive half-percentage-point cut, according to CME Group's FedWatch tool. The Fed has kept its policy rate in the 5.25%-5.50% range for the past year.