The S&P 500 ended little changed on Wednesday, with technology shares gaining but investors nervous about Middle East tensions and more US labour data due this week.

Nvidia shares rose 1.6 percent, helping to lift the S&P 500 technology index. However, Tesla shares fell 3.5 percent after the electric carmaker reported third-quarter vehicle deliveries below estimates.

Investors monitored Mideast news after Israel and the US vowed to strike back following Iran's attack on Israel on Tuesday. US President Joe Biden said on Wednesday he would not support any Israeli strike on Iran's nuclear sites in response to its missile attack and urged Israel to act "proportionally."

Data released early on Wednesday showed US private payrolls increased more than expected in September, further evidence that the labour market is not deteriorating. Investors remained focused on September non-farm payrolls data due on Friday, while US jobless claims data is due on Thursday.

"We have the jobs report Friday, and then earnings season starts at the end of next week," said Michael O'Rourke, chief market strategist at JonesTrading in Stamford, Connecticut.

"We're near all-time highs, and we know we have a friendly Fed out there. Before they push stocks to another round of new highs, investors want to hear some positive commentary from companies. People like that the Fed is very dovish and they are just waiting for another reason to push prices higher."

The Dow Jones Industrial Average rose 0.09 percent, to 42,197. The S&P 500 gained 0.01 percent, at 5,710 and the Nasdaq Composite edged up 0.08 percent, to 17,925.

JPMorgan Chase and other big banks will kick off S&P 500 third-quarter earnings season on October 11.

A strike by 45,000 dockworkers halting shipments at US East Coast and Gulf Coast ports entered its second day on Wednesday with no negotiations scheduled between the two sides. The dockworkers' strike is costing the economy roughly US$5 billion per day, JPMorgan analysts estimated.

Among declining shares, Nike dropped 6.8 percent after the athletic footwear and apparel maker withdrew its annual revenue forecast just as a new chief executive is set to take charge. (Reuters)