"As soon as a vaccine is approved, my administration will deliver it to the American people immediately. Distribution will begin 24 hours after notice," Trump said during the Friday news conference.
He said the government will have enough vaccines to distribute to every American by April.
The president's recent statements on vaccine readiness contradict the government's top health experts.
Dr. Robert Redfield, head of the Centers for Disease Control and Prevention, had predicted that a vaccine would be available to the general public sometime in the spring or summer of 2021, a statement Trump rebutted by calling Redfield "confused."
He also said any vaccine available in November or December would be in "very limited supply," and reserved for first responders and people most vulnerable to COVID-19.
Multiple vaccine candidates deployed aggressive testing measures since the COVID-19 pandemic took hold of the nation in March.
At the moment, vaccines are still being tested in human subjects, and some health experts have said they believe a safe and highly effective vaccine is several months way, if not much longer.
The entire vaccine enterprise faces continued public skepticism. Only about half of Americans said they'd get vaccinated in an Associated Press-NORC poll taken in May.
The Associated Press contributed to this report.