US stock index futures have tumbled as fears over a new strain of the coronavirus that has shut down much of Britain overshadowed a $US900 billion ($A1.2 trillion) stimulus package deal.

The strain, which is said to be up to 70 per cent more transmissible than the original, forced major European countries to shut their borders with the UK and sowed fears of further economic disruptions.

Travel stocks fell in premarket trading, with Delta Air Lines Inc, United Airlines Holdings Inc and American Airlines Group Inc slumping between 4.8 per cent and 5.3 per cent. Cruise operators Royal Caribbean Cruises, Carnival Corp and Norwegian Cruise Line Holdings fell between 8.4 per cent and 9.5 per cent.

The CBOE Volatility Index, also known as Wall Street’s “fear gauge”, jumped 29.7 points to its highest level since early November.

At 6:22 am ET, Dow e-minis were down 588 points, or 1.95 per cent, S&P 500 e-minis were down 80.5 points, or 2.17 per cent, and Nasdaq 100 e-minis were down 176.5 points, or 1.39 per cent.

US congressional leaders reached an agreement on Sunday on a $US900 billion ($A1.2 trillion) package to provide fresh aid to the virus-stricken economy, with the bill likely to be voted into effect later on Monday. Optimism over the bill had seen Wall Street indexes reach record highs last week.

Bank of America Corp, Morgan Stanley, Citigroup Inc, Goldman Sachs JPMorgan Chase & Co rose between 1.3 per cent and 2.9 per cent after the US Federal Reserve highlighted strong capital levels at the banks in the results of its second “stress test” for 2020.

Electric-car maker Tesla Inc, which has soared more than 730 per cent so far this year, fell 5.7 per cent ahead of its much anticipated debut into the benchmark S&P 500 index.

Lockheed Martin Corp fell 1.6 per cent after it agreed to buy US rocket engine manufacturer Aerojet Rocketdyne Holdings Inc for $US4.4 billion ($A5.9 billion). Shares of Aerojet Rocketdyne were up 27.3 per cent.

Planemaker Boeing Co slipped 6.7 per cent on a US Senate report saying Boeing officials “inappropriately coached” test pilots during recertification efforts.