More than 200,000 Americans have died after contracting coronavirus, more than anywhere else in the world.
"It would be 200 million people because you would have been late on the draw," the president said without evidence as he sparred with his rival during their first presidential debate.
"You would have been much later" to ban people travelling from China, Mr Trump continued.
The president claimed that placing travel restrictions on visitors from the country where the virus began had helped prevent infections.
Mr Biden criticised Mr Trump’s response to the pandemic, making the point that the US is still recording roughly 40,000 new cases a day.
Referencing Mr Trump’s comments to Bob Woodward that he downplayed the seriousness of the virus to avoid creating a panic, Mr Biden said: “You don’t panic, he panicked.”
The candidates were asked why American people should trust them to deal with the public health crisis.
"The president has no plan," Mr Biden began by saying.
The Democratic challenger argued that Mr Trump could not be trusted to lead the country’s response to Covid-19, stating that the president previously suggested Americans could protect themselves from coronavirus by ingesting disinfectants.
Mr Trump hit back by claiming that the comment had been made “sarcastically.”
The US leader then promised a vaccine would be available “soon.”
The Centres for Disease Control and Prevention previously said a vaccine would not be widely available to the American public until mid to late 2021.