Sir Mo Farah has insisted he will only look to run the marathon at the 2020 Olympics if he believes he can reach the podium.
The 34-year-old was speaking after receiving his knighthood from the Queen at Buckingham Palace on Tuesday.
Four-time Olympic champion Farah retired from the track in August to focus on road racing and has been non-committal on his Olympic future so far having also hinted he may not wear the GB jersey again.
"If I'm capable of getting a medal or close to a medal (in Tokyo), you will see me," said Farah, now coached by Paula Radcliffe's husband Gary Lough.
He has been retained on British Athletics' World Class Performance Programme despite doubts over his Olympic plans.
But, now living in London after splitting from controversial coach Alberto Salazar, Farah is eager to succeed in the London Marathon.
He said: "For me it is the biggest marathon in the world, and it is going to be tough. Mo Farah ain't going to turn up and win...it's going to be hard to run."
Also quizzed on whether he had taught the Queen to do the Mobot, letting out a loud chuckle, he said no as it is "far too rude - not in Buckingham Palace".