A Reuters/ Ipsos poll of 1,804 likely voters between 26 August and 1 September found 40 per cent support for Trump, versus 39 per cent for Clinton.
Support for Democrat Clinton has dropped steadily in recent weeks, with an eight-point lead in the poll now erased.
Reuters reported that polls in the US have produced widely different results, and a reason for this one displaying a different result to others was its focus on people who are likely to vote.
Trump has been boosted by a six percentage point jump in support from Republicans to 78 per cent in recent weeks, Reuters said.
But this is still below the 85 per cent enjoyed by Mitt Romney in the summer of 2012.
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