US President Donald Trump has accused former President Joe Biden of allowing 21 million illegal immigrants into the country, "one of the most dangerous places on earth."

The US president said that immigrants have taken jobs, wasted billions on welfare, and turned cities like Springfield, Ohio, into "nightmares."

Trump stressed that he has promised the largest mass deportation in US history and that he has a "historic mandate" to do so, with broad public support.

"Biden has allowed 21 million undocumented, illegal immigrants into the country from some of the most dangerous and dysfunctional countries in the world, many of them rapists, murderers, and terrorists. This wave of illegal immigrants has destroyed America's public schools, hospitals, parks, community resources, and livelihoods.

They have taken American jobs, squandered billions on welfare, and turned once-peaceful communities like Springfield, Ohio, into Third-World nightmares. I ran on an agenda to carry out the largest mass deportation in US history, and I have a historic mandate to do so.

Polls show overwhelming public support for ridding our country of illegal immigrants, and that is precisely what we will do. As commander in chief, I will always protect and support the heroes of ICE and Border Patrol, whose work has already secured the most secure border in this country's history. Anyone who attacks an ICE officer or Border Patrol agent will go to jail.

And those who are here illegally must either voluntarily leave using the CBP Home app, or ICE will find you and deport you. "Saving America is non-negotiable," Trump wrote on social media.