Most Asian stocks struggled higher on Monday, but investors were rattled by news that the FBI is planning to review more emails related to Democratic presidential candidate Hillary Clinton's private server, just a week before the election.
European markets also looked set for a shaky start, with financial spreadbetter CMC Markets expecting Britain's FTSE 100, France's CAC 40 and Germany's DAX to all open down 0.1 percent.
The Mexican peso, which strengthens along with the chances for a Clinton win, remained weak, while the US dollar edged up against other major currencies.
"There seems little doubt that a Trump victory would trigger selling in stock markets from current levels," Rick Spooner, chief market analyst at CMC Markets in Sydney, wrote in a note.
"This has traders nervous as they start the week assimilating fresh news on Hillary Clinton's email problems."
Bloomberg reported that Asian energy stocks fell with oil after the world's biggest crude producers failed to agree on supply cuts, while rising metals prices in China spurred gains in mining shares.
Gold was buoyed by haven demand following the FBI probe.
"Until the election, the general theme will be uncertainty, which will have implications not just on the stock market, but on the dollar and Treasuries," Chad Morganlander, a money manager in Florham Park, New Jersey at Stifel, Nicolaus & Co, which oversees about $180 billion, told Bloomberg.
"The probability that was factored into the market and the global financial system was a Hillary Clinton victory -- investors now need to square their books going into the election based on whatever new odds come out."