US stocks open slightly lower

US stocks opened slightly lower Thursday as the market took a breather from the aggressive buying that has characterized most of 2013 so far.

Five minutes into trade, the Dow Jones Industrial Average was 14.86 points (0.11 percent) lower at 13,971.66.

The S&P 500 index dropped 0.28 point (0.02 percent), while the tech-rich Nasdaq Composite Index fell 0.20 point (0.01 percent).

Thursday's trading followed a middling session Wednesday where markets concluded the day little-changed.

The S&P 500 is already up six percent this year "and there has been a litany of warnings from pundits that the market is due for a pullback," said analyst Patrick O'Hare.

"The latter view, however, has often been couched with the acknowledgment that there is a lot of frustrated money on the sidelines waiting to buy on weakness," O'Hare added.