Republican presidential candidate Donald Trump has pulled into an effective tie with Democratic rival Hillary Clinton.

According to the latest Reuters/Ipsos poll, this erases a substantial deficit, with Trump consolidating support among his party’s likely voters.

The poll showed 40 per cent of likely voters supporting Trump and 39 per cent backing Clinton for the week of August 26 to September 1.

Clinton’s support has dropped steadily in the weekly tracking poll since August 25, eliminating what had been a eight-point lead.

Trump’s gains came as Republican support for their party’s candidate jumped by six percentage points over the past two weeks, to about 78 per cent.

That is still below the 85 per cent support Republican nominee Mitt Romney enjoyed in the northern summer of 2012, but the improvement helps explain Trump’s rise in the poll.

The Reuters/Ipsos poll is conducted online in English in all 50 states.

The latest poll surveyed 1,804 likely voters over the course of the week; it had a credibility interval, a measure of accuracy, of three per cent.

In a separate question in the poll that included alternative-party candidates, Clinton and Trump were tied at 39 per cent.

Clinton: under fire for handling of classified information. Photo: Getty

Seven per cent supported Libertarian candidate Gary Johnson and two per cent supported Jill Stein of the Green Party.

Polling aggregators, which calculate averages of major polls, have shown that Clinton’s lead has been shrinking for the past few weeks.

Those averages put her advantage over Trump at between three and six percentage points. Some of the more recent individual polls, however, have the race even tighter.

In recent weeks, Clinton has come under renewed criticism over her handling of classified information while serving as US secretary of state, and her family’s charitable foundation has come under fresh scrutiny for the donations it accepted while Clinton served in the Obama administration.

Meanwhile, Clinton hasn’t been campaigning as actively as Trump.

Clinton has led Trump through most of the campaign for the November election, though neither candidate appears to have inspired the country.