Joe Biden appeared to struggle to get his words out just minutes into his historic showdown with Donald Trump.

The 81-year-old was discussing Medicare before appearing to lose his trail of thought.

Trump glared over at his opponent but held back from commenting on his apparent brain freeze.

Biden's team harboured concerns about potential gaffes going into the debate

Biden was commenting on the contribution made by billionaires on taxes and on childcare.

“If we finally beat Medicate”, he said, before being interrupted by host Jake Tapper.

“He did beat Medicare. He beat it to death”, Trump chimed in. “He’s destroying Medicare.”

Trump also accused Biden of nearly “wiping out” social security because of the “millions” of migrants at the southern border.

“What’s happened to our country is not to be believed”, he added.

The pair went on to discuss national debt soaring to record heights in the last eight years.

Trump continued to champion tax cuts he made under his leadership, saying they “spurred the greatest economy that we’ve seen”.

He added that when taxes are cut, the US took more in revenue and companies were as a result investing “trillions of dollars” back into the country.