NEW YORK, March 21 (Xinhua) -- U.S. stocks opened lower Wednesday as investors were awaiting the closely-watched Federal Reserve decision on monetary policy due out later in the day.

Shortly after the opening bell, the Dow Jones Industrial Average lost 21.69 points, or 0.09 percent, to 24,705.58. The S&P 500 decreased 4.02 points, or 0.15 percent, to 2,712.92. The Nasdaq Composite Index was down 16.04 points, or 0.22 percent, to 7,348.27.

The Fed is scheduled to announce its decision at 2 p.m.(1800 GMT) Market expectations for a March rate-hike are 94.4 percent, according to the latest data from CME Group's FedWatch tool.

While most market participants expect the Fed to raise rates by 25 basis points, they will also pay close attention to Jerome Powell's first news conference as the Fed chair and look for clues about whether the central bank will stay on track to hike three times this year.

In corporate news, shares of Facebook decreased over 2 percent on Wednesday after plunging nearly 9 percent in the previous two sessions, after reports showed that the social media giant allowed third parties to access data on millions of users without their knowledge.