Stocks dipped on Friday on geopolitical worries after the sinking of a South Korean naval ship, while a drop in Oracle's stock weighed on the tech sector.

Stocks slipped into negative territory after midday, sharply reversing their advance for a second day.

News of a Korean navy ship sinking hit sentiment, analysts said, even though South Korea's government said it was not clear if North Korea was involved in the incident. The Korean ship incident overshadowed optimism stirred earlier in the day by news that European Union leaders had agreed on a standby aid package for Greece.

That's got people's attention right now. Aside from that, we're seeing very low volume. It kind of feels like a buyers' strike, said Dave Lutz, managing director with Stifel Nicolaus Capital Markets in Baltimore.

Analysts said stocks also were pulling back after their recent strong run, with the S&P 500 up 5.5 percent for the month so far.

Oracle's stock fell 2.3 percent to $25.43, a day after the company posted strong results. Analysts said investors took profits in the stock, which had gained ahead of the earnings report. The S&P technology index <.GSPT> fell 0.3 percent.

The Dow Jones industrial average <.DJI> was down 1.20 points, or 0.01 percent, at 10,840.01. The Standard & Poor's 500 Index <.SPX> was down just 0.55 of a point, or 0.05 percent, at 1,165.18. The Nasdaq Composite Index <.IXIC> was down 6.80 points, or 0.38 percent, at 2,390.61

Euro-zone leaders unveiled a deal late Thursday in which Athens would receive coordinated bilateral loans from other euro-zone countries and the International Monetary Fund if it faced severe difficulties.

The euro-zone agreement relieved uncertainty about the European Union dealing with the problem.

(Additional reporting by Ellis Mnyandu; Editing by Jan Paschal)