Outgoing UKIP leader Nigel Farage is to address supporters of Donald Trump at a campaign rally in Mississippi later.
He will appear before 15,000 activists in Jackson, although it is unclear whether he will share the stage with the Republican presidential nominee.
Mr Farage told local radio in the state that the similarities between Brexit and the US election were "uncanny".
Mr Trump, who is trailing his rival Hillary Clinton in the opinion polls, backed the UK's exit from the EU.
In a tweet last week, Mr Trump said: "They will soon be calling me Mr Brexit."
Mr Farage, who attended the Republican convention in Cleveland last month, said he would not "fall into the trap" of personally endorsing Mr Trump in his quest to reach the White House, but added that he would not vote for Mrs Clinton "even if you paid me".
For Donald Trump, the British Brexit vote is a harbinger of a political revolution that will soon crash on to American shores.
The Republican nominee said as much as he stood on his Scottish golf course the day after the UK voted to leave the EU.
"People are angry all over the world," he said. "This will not be the last."
So, although the venue - deeply conservative Mississippi - is a bit unusual during the heat of a presidential campaign, Mr Trump possibly sharing the same stage with the man who spearheaded the Brexit vote should not be too surprising.
Mr Trump, in having Mr Farage recount his "Brexit story" to thousands of supporters on Wednesday night, probably hopes the tale of an upstart victory, despite seemingly long odds, will make his side forget about the opinion polls showing him trailing both nationally and in key battleground states.
During a radio interview on Wednesday, Mr Farage said he would tell Mr Trump's audience that the similarities between Brexit and the US election were "uncanny".
"They all said it couldn't happen," he said. "We were wasting our time. With a well-aimed stone, we hit that big Goliath and knocked it over."
Speaking on Super Talk Radio in the US state, Mr Farage said he had been part of a "political revolution" in the UK and there were the makings of a similar movement in the US.
'Fight for change'
He compared the federal government in Washington DC to the European Commission, saying many people felt it had become "its own country", and claimed the Democrat nominee epitomised the status quo.
"I'm going to say to people in this country that the circumstances, the similarities, the parallels, between the people that voted Brexit and the people that could beat Clinton in a few weeks' time here in America are uncanny.
"And if they want things to change, they've got to get up out of their chairs, go out, and fight for it. It can happen."
He suggested it did not matter that the political establishment, including many top Republicans, were shunning Mr Trump's campaign.
"Because there are millions of people out there who never voted for the Bushes, who never voted for the Clintons, who haven't voted for anybody, but who may, if they think in this presidential election they can actually change their lives and their communities, and that's the audience that matters."
Mr Farage, who is credited with securing the referendum on the UK's membership of the EU and helping to pull off the surprise Leave victory, is standing down next month as the party's figurehead after fulfilling his lifelong political ambition, but will remain as a member of the European Parliament.
UKIP donor and strategist Arron Banks, who is travelling with Mr Farage, suggested on social media that he would be having dinner with Mr Trump and was looking forward to the rally.
But Mr Farage's association with Mr Trump has not gone down well with some senior members of UKIP, including its sole MP Douglas Carswell, who tweeted "it's all going a bit South Thanet for the US Republicans" - a reference to Mr Farage's failed attempt to win a seat in the Kent constituency last year.
And Suzanne Evans, the former UKIP policy chief currently suspended by the party, suggested Mr Farage was trending on Twitter "for all the wrong reasons".
