NEW YORK (Reuters) - U.S. stocks ended flat in a volatile session on Thursday as energy stocks rebounded and investors bought beaten-down shares, especially small caps.

The S&P broke a three-day string of losses, recovering from a drop of as much as 1 per cent, to close with the slimmest of gains. Earlier, it had briefly dipped below its 150-day moving average, a level it hasn't closed below since November 2012.

The Dow Jones industrial average fell 3.66 points, or 0.02 pe rcent, to 16,801.05, the S&P 500 gained 0.01 points to 1,946.17 and the Nasdaq Composite added 8.11 points, or 0.18 per cent, to 4,430.20.

In late trading, investors temporarily set aside worries about weak economic growth and rich valuations that have hit stocks of late and added to volatility.

Markets had been pressured early after a press conference by European Central Bank head Mario Draghi, whose discussion of additional stimulus for the euro zone disappointed some investors. European stocks finished with steep losses.

Friday's market direction will likely be determined by the September jobs report, expected to show 215,000 jobs added. The number of Americans filing new claims for unemployment benefits unexpectedly fell last week, pointing to a stronger labor market.