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".
British runner Sir Mo Farah has completed his final track race in Great Britain by winning the 3000m at the Birmingham Grand Prix.Read the full story ›
Sir Mo Farah has accused the media of trying to "destroy" his legacy and career over allegations his coach breached anti-doping regulations.Read the full story ›
The 34-year-old missed out on gold in the 5,000m, but was smiling as he struck his iconic pose on top of the London Eye.Read the full story ›
Sir Mo Farah retained his 10,000 metre World Championship title with victory on the track at the London Stadium.Read the full story ›
A leaked report revealed the Olympics legend received an infusion of a controversial supplement before his London Marathon debut in 2014.Read the full story ›
Sir Mo Farah said he is "relieved" he can travel back to his family in the US after British dual nationals were given exemption from Donald Trump's travel ban to the country.
In response to the news, the Somalian-born British athlete's agent released a statement saying he was "grateful to the FCO for urgently clarifying the situation."
"Mo is relieved that he will be able to return to his family once his current training camp concludes, however, as he said in his earlier statement, he still fundamentally disagrees with this incredibly divisive and discriminatory policy," he said.
British Olympic champion Sir Mo Farah has said Donald Trump's travel ban is "deeply troubling".
The Somalia-born four-time Olympic champion could be affected by the ban, which targets those from Iraq, Iran, Libya, Somalia, Sudan, Syria and Yemen, and could affect UK citizens born abroad.
In a statement, Sir Mo Farah, who was born in Somalia, said:
On 1st January this year, Her Majesty The Queen made me a Knight of the Realm. On 27th January, President Donald Trump seems to have made me an alien.
I am a British citizen who has lived in America for the past six years - working hard, contributing to society, paying my taxes and bringing up our four children in the place they now call home.
Now, me and many others like me are being told that we may not be welcome.
It's deeply troubling that I will have to tell my children that daddy might not be able to come home - to explain why the president has introduced a policy that comes from a place of ignorance and prejudice.
I was welcomed into Britain from Somalia at eight-years-old and given the chance to succeed and realise my dreams.
I have been proud to represent my country, win medals for the British people and receive the greatest honour of a knighthood.
My story is an example of what can happen when you follow polices of compassion and understanding, not hate and isolation.
Sir Mo grew up in London from the age of eight and now lives and trains in Portland, Oregon, with his wife and four children.
The athlete's agent said although he was born in Somalia, he does not have dual nationality or hold a Somalian passport. She added: "We are seeking to clarify the situation with the US authorities."
Four-time Olympic gold medallist Mo Farah felt being awarded a knighthood in the New Year Honours was a "dream come true".Read the full story ›