Donald Trump admitted it was a "very hard thing to concede" electoral defeat but committed to leaving the White House if the Electoral College votes for Joe Biden, the Democrat president-elect as he attended a Thanksgiving event on Thursday.
"It's going to be a very hard thing to concede because we know there was massive fraud," Mr Trump said, refusing to say whether he would attend Mr Biden's inauguration in January.
In the nearest he has come to a concession, Mr Trump said he would leave the White House if Mr Biden is certified the election winner by the Electoral College - the process by which presidents are elected - on December 14.
However, Mr Trump appeared to suggest he still held hopes of retaining the presidency. Asked about his plans for his last Thanksgiving in the White House, the president told reporters that the occasion might be the “first one of a second term”.
The president added there were "a lot of things happening between now and January 20th [inauguration day]" and the election results have a "long way" to go.
"I know one thing Joe Biden did not get 80 million votes," he said. "The only way he got 80 million votes is through massive fraud."
During his annual Thanksgiving call with US troops overseas, Mr Trump also claimed the US will begin delivering Covid-19 vaccines "next week and the week after" as he insisted the country had "rounded the curve" on the pandemic.
"We are rounding the curve [on the virus]. The vaccines are being delivered - literally it will start next week and the week after," he said during his address.
Mr Trump suggested that medical workers, other frontline staff and elderly people would be the first to receive the vaccinations.
It is unclear which vaccine Mr Trump was referencing, or whether he was referring to a specific federal government policy for a vaccine distribution.
Two US companies, Moderna and Pfizer, have so far announced that their vaccines are effective at protecting people against coronavirus.
Earlier this week US government officials said the administration planned to distribute around 6.4 million doses of Pfizer's vaccine to Americans as soon as the jab received emergency approval from the federal government, expected to be around mid-December.
Officials say that by the end of the year they expect to have enough doses of vaccines from both Pfizer and Moderna to vaccinate around 20 million people.
However, it is likely to be April before the vaccines are distributed to the wider American public.
In his address on Thursday, Mr Trump praised the speed with which a vaccination had been created, saying "two companies already announced [successful vaccines]" adding that several others were "coming up soon".
"Some people have called it a medical miracle," the president said adding that the hunt for a vaccination "could have taken four or five years".