NEW YORK (AFP) - Wall Street stocks dipped on Tuesday (Sept 4) on continued worries about US trade conflicts even as Amazon briefly topped US$1 trillion (S$1.3 trillion) in market value in the latest demonstration of US tech industry dominance.

The Dow Jones Industrial Average slipped 0.1 per cent to 25,952.75.

The broad-based S&P 500 dipped 0.2 per cent to 2,896.71, while the tech-rich Nasdaq Composite Index declined 0.2 per cent to 8,091.25.

Investors were eyeing the latest in the ongoing trade fight between the US and Canada after President Donald Trump again threatened over the holiday weekend to leave Canada out of a revamped North American Free Trade Agreement.

Talks with Ottawa are set to resume in Washington on Wednesday to try to salvage the three-nation Nafta, although Trump has said he could proceed with Mexico alone.

Analysts also are monitoring the state of trade relations between Washington and Beijing, with the possibility of a new wave of punitive tariffs hitting as soon as this week.

Meanwhile, Amazon hit a milestone when it briefly topped US$1 trillion in market capitalisation about one month after Apple achieved the feat. It pulled back somewhat and shares finished up 1.3 per cent.

But Facebook fell 2.6 per cent following a downgrade by MoffetNathanson, while Tesla Motors dropped 4.2 per cent following a note from Goldman Sachs warning the company faced rising competition from car companies that are launching new electric vehicles.

Dow member Nike fell 3.2 per cent amid worries the new advertising campaign featuring Colin Kaepernick will backfire on the sports giant.

Kaepernick has been benched from playing American football after kneeling during the US national anthem in 2016, launching a movement to protest racial injustice.

He appears as the new face of Nike's "Just do it" campaign.