US presidential candidates Hillary Clinton and Donald Trump are neck-and-neck in a new national tracking poll released on Tuesday.

The latest ABC News/The Washington Post poll showed Trump barely edging Clinton among likely voters, 46 per cent to 45 per cent, well within the poll's 3 percentage point margin of error, said a CNN report.

However, according to a model from Moody's Analytics that has accurately predicted the last nine US presidential contests, Democrat Hillary Clinton will win the White House in next week's election.

Clinton is forecast to get 332 Electoral College votes against 206 for Republican Donald Trump, Moody's Analytics predicted.

The Reuters-Ipsos States of the Nation project also predicts a Clinton win, with a 95 percent probability of her winning at least 278 electoral votes. A candidate needs to win at least 270 electoral votes to be elected president.

Asian shares tumbled to seven-week lows and the dollar was on the defensive following polls suggesting that the US presidential election race was tightening. The voting will be held on November 8.

Investor anxiety has deepened over a possible Trump victory given uncertainty on the Republican candidate's stance on several issues including foreign policy, trade relations and immigrants, while Clinton is viewed as a candidate of the status quo, Reuters said.

Support for Libertarian Party nominee Gary Johnson, meanwhile has fallen to a new low, according to the poll, plunging to just 3 per cent nationwide. Green Party candidate Jill Stein is at 2 per cent, it said.

Although Trump's single-point advantage over Clinton is statistically negligible, it is his first lead in an ABC/Post poll since May, said CNN.

This perhaps is giving hope to the Republican presidential nominee's supporters, who believe their candidate's prospects were bolstered last week with the revelation that the FBI is reviewing new emails found on the laptop of Anthony Weiner, the former congressman and estranged husband of top Clinton aide Huma Abedin.

Clinton still leads Trump in the CNN Poll of Polls, an average of the five most recent national phone polls, including Tuesday's ABC/WaPo tracking survey, 46 per cent to 42 per cent.