By the end of the day, the Dow Jones index fell 59.44 points or 0.29% to 20,591.86, while the S&P 500 was down 8.85 points or 0.38% at 2,344.93.

The tech-focused Nasdaq index dropped 30.61 points or 0.52% to 5,836.16.

Financial stocks did particularly badly ahead of results from Wells Fargo, Citigroup and JPMorgan on Thursday.

The S&P 500 financials index slipped 0.9%, with Wells and Citi losing 1.92% and 0.88% respectively. JP Morgan gained 0.33%.

Shares in United Airlines continued to tumble as boss Oscar Munoz said he would not step down over the forcible removal of a passenger from a flight.

The stock ended 1.10% lower after losing 1% yesterday.