Donald Trump has warned Americans the country will be ‘flooded with refugees’ if Joe Biden wins the election in November.

During a campaign speech in Michigan, the 74-year-old also labelled the Democrats ‘far-left lunatics’ who will take the US to a place where crime will rage ‘like never before’.

Michigan voted Republican for the first time in 28 years at the 2016 election, but polls are currently suggesting Biden could take the mid-west state back in two months time.

"On November 3, Michigan you better vote for me! I got you so many damn car plants," Trump told the crowd.

"He's (Biden) promised to flood your states with refugees. He would open up the floodgates amid a pandemic and by the way the wall is over 311 miles long right now.

"The murder rate in Democrat-run cities like Chicago, Baltimore, New York [and] so many others is higher than in Afghanistan, yet Biden supports imposing these failed policies nationwide. You will have crime like you've never seen it before.

"If Joe Biden is elected far-left lunatics won't just be running frail Democrat cities, they'll be running the Department of Justice, the Department of Homeland Security and the US Supreme Court, and we can't let that happen.

"No city, town or suburb will be safe. On November 3 your vote will save America. Remember it's the most important elect we've ever had."

Trump also spoke about how his wife Melania thought Biden looked ‘sad’ during a Democratic debate in a bizarre insult towards his presidential rival.

He added: “The first lady actually came in... and she watched the debate and she watched Joe and she said, ’Darling, it's so sad’.”

His comments towards Biden come just 24 hours after the President’s former aide labelled him a ‘full-blown lunatic’.