NEW YORK (AFP) - US stocks closed mostly flat on Tuesday, except for a solid gain on the Nasdaq, as investors awaited the outcome of a Federal Reserve monetary policy meeting.

At the closing bell, the Dow Jones Industrial Average was up 1.30 (0.01 per cent) at 15,523.27.

The broad-based S&P 500 added 0.82 (0.05 per cent) at 1,686.15, while the tech-rich Nasdaq Composite Index solidly outperformed, gaining 17.33 (0.48 per cent) at 3,616.47.

The Dow and the S&P 500 drifted in and out of positive territory after Monday's losses, while the Nasdaq maintained gains throughout the session.

The action came as the Federal Reserve opened a two-day monetary policy meeting expected to provide no new direction but perhaps clues to the Fed's thinking on winding down massive stimulus.

"Typically, the stock and bond markets are calm during meeting days as traders wait for the Fed's policy statement, scheduled for release at 2pm (1800 GMT) tomorrow," said Fred Dickson, chief investment strategist at Davidson Companies.