Wall Street opens lower as Apple falls 2% on old iPhone sale ban in China

US equity futures fell in a volatile session on Monday, with a drop in Apple Inc's shares curbing the market's attempts to stage a bounce back from its worst week since March on worries over global growth and the China-US trade war.

After hitting six-month lows earlier in the session, stock futures briefly turned higher, which appeared to coincide with British Prime Minister Theresa May's abrupt decision to pull a parliamentary vote on her Brexit deal.

But that bounce was short-lived as Apple fell 2 per cent in premarket trading after Qualcomm Inc said it had won a preliminary order from a Chinese court banning the importation and sale of several iPhone models in China due to patent violations.

At 9:14 am ET, Dow e-minis were down 52 points, or 0.21 per cent. S&P 500 e-minis were down 4 points, or 0.15 per cent and Nasdaq 100 e-minis were down 15.25 points, or 0.23 per cent.

Wall Street continues to be dogged by signs of cooling growth and worries that escalating tensions between the United States and China could scuttle their fragile trade truce.

"We are hard-pressed to pick a key direction in premarket trading that's really going to hold with the amount of damage we've done to markets over the course of the past week," said Art Hogan, chief market strategist at B. Riley FBR in New York.

The three main indexes slid 4.5 per cent or more last week in their biggest weekly tumble since March, pushing the benchmark S&P 500 and the blue-chip Dow Jones Industrial Average into the red for the year.