Equities on both sides of the Atlantic fell overnight, along with oil and gold, while the US dollar climbed to a 14-month high against the euro on optimism about the American economy and concern about a vote for Scottish independence.
A poll showed that supporters of Scottish independence are gaining traction ahead of a September 18 referendum. A YouGov survey for the Sunday Times newspaper showed 51 per cent approved of Scotland's independence from the United Kingdom.
"The speed with which the polls have flipped has clearly been a shock to a lot of people," Adam Myers, European head of FX strategy at Credit Agricole in London, told Reuters.
The British pound tumbled, sliding 1.3 per cent against the greenback.
"If they were to vote 'Yes' then sterling could drop another 10 per cent so the tail risk is big," Graham Davidson, a foreign-exchange trader at National Australia Bank in London, told Bloomberg News.
The US dollar also benefited from the optimistic view on the US economy, while elsewhere-in China and Europe-the pace of growth is faltering.
Last Friday's jobs report, while showing the pace of growth in US payrolls fell short of expectations for August, failed to alter the view that the American economy continues to gather steam.
"Other indicators are still showing that the US economy will strengthen in the second half of this year," Martin Schwerdtfeger, a foreign exchange strategist at TD Securities in Toronto, told Reuters. "The payroll number did not change that."
In late afternoon trading in New York, the Dow Jones Industrial Average fell 0.25 per cent, the Standard & Poor's 500 Index dropped 0.49 per cent and the Nasdaq Composite Index slipped 0.12 per cent.
Declines in shares of Exxon Mobil and Wal-Mart, down 1.6 per cent and 1.3 per cent respectively, led the Dow lower.
Oil slid, pushing Brent crude below US$100 a barrel for the first time since 2013, amid concern that weakness in China and Europe will hurt demand.
Shares of Boeing jumped, last up 2. 8 per cent, after Ryanair said it agreed to buy up to 200 new Boeing 737 MAX 200 aircraft worth up to US$22 billion at current list prices.
In Europe, the Stoxx 600 ended the session with 0.4 per cent drop from the previous close. The UK's FTSE 100 Index and France's CAC 40 both fell 0.3 per cent. Germany's DAX rose 0.1 per cent.
A report showed that China's imports posted a surprise drop last month, declining 2.4 per cent from a year earlier, and underpinning concern about the world's second-largest economy. Exports rallied 9.4 per cent.
"Global oil demand remains soft," John Kilduff, a partner at Again Capital, a New York-based hedge fund that focuses on energy, told Bloomberg News. "China's imports being down are another sign of softening. Any sign of a slowdown there has a major impact on the market.
Meanwhile, Barclays cut 2,700 jobs in its investment bank this year as part of a plan unveiled in May to axe 7,000 positions over three years, the head of the business, Tom King, said on Monday, according to Reuters