Mo Farah is increasingly confident he can reach Tokyo 2020 as he prepares to launch his marathon career.
The four-time Olympic champion has been training in Ethiopia but will race in the Vitality Big Half in London on Sunday.
Farah is yet to make a decision over whether he will run the marathon for Team GB in Japan as he gets to grips with the new career on the road.
But, ahead of the 'soft launch' of his marathon running on the new 21km course, he continued to refuse to rule out a return to the Olympics having quit the track last year.
"If you're not mixing with the guys and being close to winning medals, it would be hard to just turn up and make up the numbers," he said.
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"I'm definitely more confident. But I ran 2.08 hours in 2014 and the aim is to improve on that. We'll see how it goes. London (Marathon in April) is a big one. It's definitely more realistic.
"But over the next couple of years the aim is to learn about the marathon and get better at it.
"Watching Birmingham (World Indoor Championships) yesterday, I do think about it. But my job is to get through the London Marathon and how knows? Maybe Tokyo 2020."
Farah is being trained by Paula Radcliffe's husband Gary Lough as he continues to develop on the road.
But the 34-year-old emphatically said he would not return to the track after ending his glittering career last year.
He won gold in the 10,000m and silver in the 5000m in London at the World Championships last summer.
"There's a point in your career where you have to make a decision. I've finished on the track and I wanted to start anew with Gary and it's going well," he said.
"He's a great coach and what he has achieved over the years with Paula is incredible.
"I wanted to be back in London and base myself here.
"You definitely won't see me on the track. I want to learn about the marathon and see what I can achieve."
