NEW YORK (AFP) - Wall Street stocks retreated on Wednesday (Aug 23) after United States President Donald Trump suggested he could shut down the US government if Congress did not fund a border wall with Mexico.

Analysts also cited profit-taking as a driver after US stocks rallied strongly on Tuesday.

But sentiment was less upbeat again on Wednesday following Mr Trump's free-wheeling speech in Arizona on Tuesday night, in which he lambasted the media and vowed to build the wall "if we have to close down our government".

"The fear of new dysfunction might be having some bearing on what the market is doing today," said Mr Bill Lynch, director of investment at Hinsdale Associates.

Analysts are also looking ahead to Friday's summit of central bankers, which comes amid unease over a shift from the easy-money policies of recent years.

The Dow Jones Industrial Average fell 0.4 per cent to 21,812.09.

The broad-based S&P 500 dropped 0.4 per cent to 2,444.04, while the tech-rich Nasdaq Composite Index lost 0.3 per cent to 6,278.41.

Wal-Mart Stores shed 0.1 per cent and Google parent Alphabet rose 0.3 per cent after the two companies announced they were teaming up in an attempt to challenge Amazon's growing dominance in online shopping through voice-activated ordering of goods on Google Express.

Home-improvement retailer Lowe's fell 3.7 per cent after reporting that second-quarter net income was US$1.57 per share, four cents below analyst expectations. Rival Home Depot, a Dow member, lost 0.5 per cent.

Salesforce rose 0.1 per cent as it projected that full-year sales would grow by more than 20 per cent from last year to about US$10.4 billion (S$14.1 billion). Second-quarter revenue jumped 25 per cent to US$2.6 billion.