U.S. stocks ended mixed on Monday prior to the Federal Reserve meeting while tech stocks lifting Nasdaq index.

The Dow Jones industrial average rose 3.76, or 0.03 percent, at 12,490.78. The Standard & Poor's 500 index was down 1.56, or 0.11 percent, at 1,420.62, and the Nasdaq composite index was up 4.96, or 0.63 percent.

Several merger news boost the markets as no major economic data came out.

Merrill Lynch agreed to acquire wealth manager First Republic Bank for 1.8 billion dollars in cash and stock and Citigroup reached an agreement to buy British insurer Prudential PLC's Egg Banking PLC online bank for about 1.13 billion dollars.

The markets couldn't find their direction ahead the Fed meeting, which is to start on Tuesday on the latest economic situation and interest rates, said analysts.