Wall Street stocks finished mixed on Wednesday as markets weighed lingering worries over Iran, while Nvidia surged to a fresh record amid continued artificial intelligence bullishness.

President Donald Trump boasted that US strikes had destroyed Iran's nuclear programme, although leaked US intelligence said the strikes had set back Tehran's nuclear programme by just a few months.

"Maybe the US bombardment didn't destroy the Iran nuclear programme," said Jack Ablin of Cresset Capital Management.

The Dow Jones finished down 0.3 percent at 42,982.

The S&P 500 was flat at 6,092, while the Nasdaq gained 0.3 percent to 19,973.

The mixed session followed two strong days for equities after conditions in the Middle East stabilised on Monday and Tuesday, with Iran and Israel agreeing to a ceasefire.

"Investors are sort of catching their breath, since we had a very strong move on Monday and Tuesday," said Sam Stovall, chief investment officer at CFRA Research.

"I think that investors are re-evaluating the US intelligence report that maybe the strike on Iran was not as successful as earlier indicated."

Stovall also noted that markets are approaching new all-time highs and "usually it takes a couple of attempts" before breaking through.

But a bright spot was Nvidia, which shot up 4.3 percent to US$154.31, giving it a market valuation of around US$3.76 trillion – more valuable than Microsoft, Apple and other tech giants.

The rise came as CEO Jensen Huang presented the company's latest technologies at Nvidia's annual meeting.

Among other companies, FedEx fell 3.3 percent after the shipping company did not provide a full-year forecast, citing uncertainty about the global trade outlook and tariffs.

Tesla dropped 3.8 percent after the company's car sales sank again in Europe last month, the latest poor result from Elon Musk's company in the region.

General Mills dropped 5.1 percent on disappointment over the company's forecast. The food giant expects a drop of 10 to 15 percent in operating profit.

But large banks had a good day with JPMorgan Chase and Citigroup winning one percent or more as the Federal Reserve proposed easing capital rule requirements. (AFP)