Wall Street stocks were mixed early Thursday following disappointing private sector US hiring data ahead of the much-anticipated monthly jobs report.

Private sector employment rose by 99,000 in August, well below the 150,000 estimated by analysts, according to payroll firm ADP.

"This is low, and if this is confirmed by tomorrow's Department of Labor report, then it's a clear indication that the job market is slowing down," said Spartan Capital's Peter Cardillo.

About 15 minutes into trading, the Dow Jones Industrial Average was down 0.2 percent at 40,912.79.

The broad-based S&P 500 added 0.1 percent at 5,524.80, while the tech-rich Nasdaq Composite Index advanced 0.5 percent to 17,165.76.

The Federal Reserve has already signaled plans to cut interest rates in light of a loosening job market.

Many analysts see the trend as consistent with an economy that is slowing but not necessarily heading into a recession; a weak jobs report Friday could challenge that view.

After Tuesday's rout, stocks veered in and out of positive territory on Wednesday. Cardillo expects another mixed session Thursday ahead of Friday's jobs report.

Among individual companies, Frontier Communications Parent fell 8.8 percent after agreeing to be acquired by Verizon for $20 billion.

Verizon, which said Frontier's fiber internet assets will enhance its broadband capacity, dipped 0.9 percent.