The Dow and S&P 500 inched higher, while the Nasdaq dipped on Wednesday after Federal Reserve officials said they were still worried about labor market weakness and a report on the services sector showed only slight improvement in the economy.

Cautious minutes from the Fed's last meeting, as well as the ISM services report, which showed the sector hovering on the cusp of expansion, came after a number of data points helped lift stocks earlier this week to their highest closing levels in more than a year.

The private-sector ADP jobs report, which showed that private-sector job losses slowed in December from November's pace, gave investors further pause for thought before Friday's key non-farm payrolls number.

The big party is Friday morning, said Stephen Massocca, managing director at Wedbush Morgan in San Francisco. Today's data points were mixed. I think that they are not that meaningful, and I think that the most important data point we will get will be Friday morning.

Even with Wednesday's tiny gain, the S&P 500 eked out a new 15-month high.

The Dow Jones industrial average <.DJI> rose 1.66 points, or 0.02 percent, to end at 10,573.68. The Standard & Poor's 500 Index <.SPX> inched up just 0.62 of a point, or 0.05 percent, to finish at 1,137.14. But the Nasdaq Composite Index <.IXIC> dropped 7.62 points, or 0.33 percent, to 2,301.09.

One bright spot was Family Dollar Stores Inc , up 12.5 percent at $30.92, after the retailer reported first-quarter earnings that beat expectations. Rival 99 Cents Only Stores climbed 5 percent to $14.02.

The Nasdaq was pushed lower by losses in big-cap technology issues, including Apple Inc , down 1.6 percent at $210.97, and Microsoft Corp , down 0.6 percent at $30.77.

Weighing on the Dow was Travelers Cos Inc , down 1.4 percent at $47.94 after FBR cut its rating on the insurer to market perform from outperform.

DJ TRANSPORTS DIVE AS OIL JUMPS

Another obstacle for stocks was the surge in the price of oil to above $83 a barrel, which pushed the Dow Jones Transportation Average <.DJT> down 0.6 percent. Energy-hungry package-shipping companies like FedEx Corp , down 0.8 percent at $83.84, and UPS , down 0.7 percent at $57.85, make up the Dow Jones Transportation Average.

U.S. February crude oil climbed $1.41, or 1.7 percent, to settle at $83.18 a barrel, the highest close since October 9, 2008, on expectations that cold weather in the United States will increase demand for heating oil.

Diversified manufacturer 3M Co rose 1.5 percent to $83.72, supporting the blue-chip Dow average after Goldman Sachs added the stock to its Americas conviction buy list and said stronger-than-expected results in October and November likely continued in December.

In contrast, Walgreen Co shed 0.8 percent to $36.72 after the drugstore chain said same-store sales fell in December instead of rising, as Wall Street had expected.

But Dow Chemical Co jumped 1.8 percent to $31.02 after Barclays Capital upgraded the stock to overweight from equal-weight.

On the economic front, the Institute for Supply Management non-manufacturing index rose to 50.1 in December, showing slight expansion, but was slightly below the 50.5 forecast by economists.

Earlier Wednesday, the ADP Employer Services report showed U.S. private employers shed 84,000 jobs in December, less than a revised 145,000 in November, but exceeding economists' forecast for a loss of 73,000 jobs.

Volume was light on the New York Stock Exchange, with 1.11 billion shares changing hands, below last year's estimated daily average of 2.18 billion. On the Nasdaq, about 2.28 billion shares traded.

Advancing stocks outnumbered declining ones on the NYSE by a ratio of 3 to 2.

But on the Nasdaq, the opposite trend held sway, with about five stocks falling for every four that rose.

(Reporting by Edward Krudy; Editing by Jan Paschal)