US President Donald Trump left Washington on Wednesday just three hours ahead of the inauguration of his successor Joe Biden, saying it had been an "incredible four years" and promising to be "back in some form."

"I just want to say goodbye but hopefully it's not a long-term goodbye," Trump said in remarks to reporters at the White House before he and First Lady Melania Trump walked a short red carpet and boarded Marine One for the helicopter ride to Joint Base Andrews.

US President Donald Trump waves as he boards Marine One at the White House for the final time
US President Donald Trump waves as he boards Marine One at the White House for the final time AFP / MANDEL NGAN

Speaking to a small crowd of supporters, staff and family members at Andrews after a 21-gun salute and a serenade of "Hail to the Chief," Trump said "this has been an incredible four years."

"We've accomplished so much together," he said. "I will always fight for you.

President Donald Trump and First Lady Melania Trump test positive for Covid-19
President Donald Trump and First Lady Melania Trump test positive for Covid-19 AFP / MANDEL NGAN

"It is my greatest honor and privilege to have been your president," he said. "We will be back in some form."

The 74-year-old Trump has hinted at running for president again in 2024, but faces a trial in the Senate over his role in the January 6 storming of the US Capitol by his supporters and a potential ban on holding office in the future.

IMAGES US President Donald Trump leaves the White House for the last time aboard the Marine One, skipping the inauguration of successor Joe Biden as the 46th US president in an extraordinary break with tradition.
IMAGES US President Donald Trump leaves the White House for the last time aboard the Marine One, skipping the inauguration of successor Joe Biden as the 46th US president in an extraordinary break with tradition. DC POOL / Sébastien VUAGNAT

Trump boarded Air Force One after his remarks and the presidential jet took off for the two-hour flight to Florida as Frank Sinatra's "My Way" played on loudspeakers on the tarmac on a sunny but chilly day.

Trump will be at his Mar-a-Lago resort in Florida when the 78-year-old Biden is sworn in at noon (1700 GMT) as the 46th president of the United States.

He is the first president in more than 150 years to snub the inauguration of his successor.

Trump did not address Biden by name in his remarks but said he wishes the new administration "great luck and great success."

Trump repeatedly and falsely claimed that he won the November 3 election and he was impeached for a second time by the House of Representatives after his supporters stormed the Capitol in a bid to disrupt the certification by Congress of Biden's victory.