Equity indexes on Wall Street gave up earlier gains amid uncertainty over the prospects for a US-China trade deal. 

Demand for US treasuries and precious metals grew, showing an appetite for less-risky investments.

The yield curve remained inverted with the spread on interest rates on three-month bills over 10-year yields hitting its widest level since March 2007. The yield curve often inverts prior to a US recession.

Gold rose as investors sought cover from worries over global economic growth and trade, while silver latched on to bullion's rally to breach the $18 an ounce mark for the first time in nearly two years.

The benchmark S&P500 index fell as investors lost some of the trade optimism that had helped boost overseas markets.

Stock markets in Asia and Europe had advanced following US President Donald Trump's comment on Monday that Chinese officials had contacted their US trade counterparts and offered to resume negotiations, an assertion China did not confirm.

"We continue to have concerns about the global economy. The US President's deal with China is pending and that may be the rhetoric from the White House as opposed to an actual fact pointing to negotiation," said Bart Melek, head of commodity strategies at TD Securities in Toronto.