* ADP private payrolls just short of expectations
* U.S. services sector readings show growth
* Energy shares rise for third session
* Indexes up: Dow 0.1 pct, S&P 0.2 pct, Nasdaq 0.2 pct (Updates to midday trading)
By Ryan Vlastelica
NEW YORK, Dec 3 (Reuters) - U.S. stocks rose modestly on Wednesday as energy-related shares rose for a third straight session and data pointed to improving conditions in the U.S. services sector, which makes up a majority of the economy.
Market moves were slight, with many traders looking ahead to a key meeting of the European Central Bank. Still, the Dow hit an intraday record and the S&P was within four points of its record set last week.
The S&P 500 energy sector rose 1.3 percent as the top-performing sector on the day, up alongside a 0.6 percent increase in the price of crude oil. Cimarex Energy was the S&P 500's top percentage gainer, up 5.9 percent at $108.98. Diamond Offshore rose 3.7 percent to $31.46.
While the sector is on track for its third consecutive daily advance - and is up 3.3 percent over that period - the group remains the year's biggest underperformer. It is the only industry group to be negative on the year, pressured as crude has lost more than 30 percent from a recent high.
"Energy is the undervalued sector of the market, but trying to call the bottom of oil prices is like trying to catch a falling knife. There's value to be had, but also might be some more pain along the way," said Joseph Quinlan, chief market strategist at U.S. Trust, Bank of America Private Wealth Management in New York.
A gauge of growth in the U.S. services sector rose more than expected in November even as its employment component dipped, according to ISM, while Markit's reading of the sector showed growth, though as a slower clip.
Markets reacted mutedly to data showing the U.S. private sector created 208,000 jobs last month, fewer than expected. The numbers, however, suggested a slowing global economy was having a limited impact on domestic activity.
Momentum is building for the ECB to launch a program of sovereign-bond buying to boost the bloc's struggling economy, with most signs pointing to March for a decision. The ECB meets on Thursday.
"We're looking for any stimulus, and are vulnerable to no additional actions being taken," said Quinlan, who helps oversee $330 billion in assets. "We'll feel more confident about global prospects if we have a more proactive ECB."
At 12:05 p.m. (1705 GMT) the Dow Jones industrial average rose 8.54 points, or 0.05 percent, to 17,888.09, the S&P 500 gained 3.81 points, or 0.18 percent, to 2,070.36 and the Nasdaq Composite added 11.55 points, or 0.24 percent, to 4,767.36.
Advancing issues outnumbered declining ones on the NYSE by 2,079 to 873, for a 2.38-to-1 ratio; on the Nasdaq, 1,772 issues rose and 823 fell for a 2.15-to-1 ratio.
The S&P 500 was posting 92 new 52-week highs and 2 new lows; the Nasdaq Composite was recording 103 new highs and 48 new lows. (Editing by Nick Zieminski)