U.S. stocks trimmed early losses and ended the session mixed on Thursday as investors weighed debt problems in Spain against positive domestic economic data.

The Dow Jones industrial average added 19.61 points, or 0.15 percent, at 13,145.82. The Standard & Poor's 500 dipped 2.26 points, or 0.16 percent, to 1,403.28. The Nasdaq Composite Index dropped 9.60 points, or 0.31 percent, to 3,095.36.

Major indexes were mired in the red for most time during the session as the situation in Spain reminded investors the crisis in Europe was far from over.

In Madrid, people took to street to protest against the government's austerity plan and clashed with police, spurring fresh concerns about the nation's spending cut outlook and underscoring the difficulty that the government has in reining in overblown spending.

Thursday's domestic economic data were also a little bit disappointing.

According to the Commerce Department, the U.S. economy expanded at a 3.0-percent annual rate in the fourth quarter of 2010, unrevised from the previous estimate. The gain, though the strongest since the second quarter of 2008, was still lower than market expectation of 3.2 percent.

Meanwhile, the Labor Department reported the number of people applying for unemployment benefits dropped 5,000 to a seasonally adjusted 359,000 last week, hitting another four-year low.

However, investors seemed not so sure about the recovery as they did in the beginning of the year, especially after the Federal Reserve Chairman Ben Bernanke said the U.S. economy was still weak.

Adding to the concerns, the latest string of data on housing and consumer sentiment failed to satisfy, making some investors more hesitate to bet on the economy, given the strong rally in the past three months.

Investors may also be waiting to see how companies did in the first quarter, to get some sense of the broader economy, as a new earnings season is about to kick off with Alcoa reporting earnings on April 10.

In other markets, the U.S. dollar traded mixed against major currencies in late New York trading while crude prices plunged as rising expectation of oil strategic reserve release triggered sell- off across the market.

Light, sweet crude for May delivery fell 2.63 dollars, or 2.50 percent to settle at 102.78 dollars a barrel on the New York Mercantile Exchange.