Wall Street stocks powered to new records again Wednesday as investors continued to shrug off lackluster US economic data amid optimism over coronavirus therapeutics and vaccines.

The S&P 500 and Nasdaq again finished at all-time highs, with the tech-rich Nasdaq closing above 12,000 for the first time.

US shares benefited from what analysts have called a "fear of missing out" on further gains amid broad investor optimism.

European stocks also had a good day, with London, Paris and Frankfurt all up more than one percent.

"Global stocks have been rising on the back of the steadily improving sentiment on Wall Street and elsewhere over the past few weeks amid falling Covid-19 death rates, falling new cases in the United States, and hopes that an effective vaccine will soon be approved," said Fawad Razaqzada at ThinkMarkets.

"Meanwhile, improving manufacturing activity in China, the US and eurozone has fuelled hopes that the recovery is well under way across the world's key economic regions."

But a report Wednesday from private payrolls firm ADP said the US private sector added 428,000 new jobs in August, a third of the amount expected by analysts. The data comes ahead of Friday's much-anticipated government employment report for August.

The Federal Reserve also offered a cautious appraisal of the US economy, noting "rising instances of furloughed workers being laid off permanently as demand remained soft," especially in the hard-hit services industries.

Home and vehicle sales were strong but "many districts noted a slowing pace of growth in these areas, and total spending was still far below pre-pandemic levels," the Fed said in its beige book survey of economic conditions.

IG analyst Chris Beauchamp noted that, "The apparent disconnect between markets and the real world gets wider and wider, fuelled by low interest rates, the prospect of more easing, but also the hope that the overall situation will continue to improve.

"Markets continue to seek the positive and ignore the negatives, but it is odd to see such relentless positivity in US markets when the pandemic has yet to subside, the economic impact is only just being felt and we have a US presidential election just a few weeks away."

But Art Hogan, chief market strategist at National Securities, said optimism about coronavirus remedies had boosted sentiment, along with broad confidence that Washington will eventually reach a deal on fiscal stimulus "although that's getting frustratingly slow."

New York - Dow: UP 1.6 percent at 29,100.50 (close)

Tech firms tracked another record on the Nasdaq, boosted by people staying at home or working from home during the coronavirus pandemic
Tech firms tracked another record on the Nasdaq, boosted by people staying at home or working from home during the coronavirus pandemic AFP / Olivier DOULIERY

New York - S&P 500: UP 1.5 percent at 3,580.84 (close)

New York - Nasdaq: UP 1.0 percent at 12,056.44 (close)

London - FTSE 100: UP 1.4 percent at 5,940.95 (close)

Frankfurt - DAX 30: UP 2.1 percent at 13,243.43 (close)

Paris - CAC 40: UP 1.9 percent at 5,031.74 (close)

EURO STOXX 50: UP 1.8 percent at 3,337.77 (close)

Tokyo - Nikkei 225: UP 0.5 percent at 23,247.15 (close)

Hong Kong - Hang Seng: DOWN 0.3 percent at 25,120.09 (close)

Shanghai - Composite: DOWN 0.2 percent at 3,404.80 (close)

Euro/dollar: DOWN at $1.1857 from $1.1912 at 2100 GMT on Tuesday

Dollar/yen: UP at 106.16 yen from 105.96 yen

Pound/dollar: DOWN at $1.3349 from $1.3384

Euro/pound: DOWN at 88.78 from 89.00 pence

Brent North Sea crude: DOWN 2.5 percent at $44.43 per barrel

West Texas Intermediate: DOWN 2.9 percent at $41.51 per barrel