Former US President Donald Trump unleashed on President Joe Biden over the weekend as he called on supporters to vote the 81-year-old out of the White House.

"This November, Virginia is going to tell crooked Joe Biden, you are fired, you are fired, get out of here," Trump told supporters at a rally on Saturday.

The Republican frontrunner also lashed out at President Biden over his lax border policies.

During a campaign speech in Virginia on Saturday, Trump accused Biden of allowing millions of migrants to enter the US from Mexico.

"Let's face it. This country is a mess. We've got 15, 16 million people that came in," Trump said.

"This November, Virginia is going to tell crooked Joe Biden, you are fired, you are fired, get out of here."