Double Olympic champion Mo Farah will run in this year's London Marathon.
But the 29-year-old Briton only intends to complete half of the 26.2-mile race as he continues to target success in both the 5,000m and 10,000m.
Farah, who said he was "excited" to be running in the event on 21 April, plans to run the full distance in the 2014 London Marathon.
But the 29-year-old told BBC Sport: "It doesn't necessarily mean a track runner can be good at marathons."
However, Paula Radcliffe, who won the women's race in London in 2002, 2003 and 2005, questioned Farah's decision.
She said: "Honestly I find it a little bit strange - it's not what I would have done.
"Either you find a good half marathon somewhere or you take the plunge and attack the distance and race it.
"Here he's caught between two stools. For me you go into the London Marathon when you're ready to do it and attack it hard. But everybody has different reasons."
Farah, who became 5,000m and 10,000m champion at the 2012 London Olympics, may also
move up to the marathon
for the 2016 Games in Rio.
The Londoner's 2013 season begins with his only indoor race over 3,000m at this weekend's
British Grand Prix in Birmingham.
Farah's training trip to Kenya
Next weekend, Farah flies out to New Orleans to compete in another half-marathon.
The Olympic star says he wants to run the same distance in London's elite marathon in April to prepare himself for the full distance next year.
"It will allow me to understand the course and the systems I will need when I run the full distance," said Farah.
"I won the London Mini Marathon when I was younger and have watched the race every year for as long as I can remember.
"As a young boy growing up in London it has always been my ambition to run the London Marathon.
"It's one of the biggest marathons in the world. It will be my pleasure to run my first marathon in London.
"I am excited and looking forward to it. You've got to go and test yourself to see what you can do."
Farah won the three-mile junior event three years in a row as a schoolboy between 1998 and 2000.
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“We know he can be very good at marathon, but we don't know he can be the best in the world ”
Mo Farah's coach
This year Farah will start the marathon as part of the elite men's field - which includes marathon world record holder Patrick Makau, Olympic champion Stephen Kiprotich and world champion Abel Kirui - and run to the half-way point.
Farah has had one eye on a switch to marathons since his
stunning double at the London Olympics
Farah's coach, Alberto Salazar, told the BBC in October
that the runner could attempt to win both the 10,000m and marathon at the Rio Olympics in 2016
"He won't go to the marathon until 2014," said Salazar. "He's the best long-distance runner on the track in the world right now.
"We know he can be very good at marathon, but we don't know he can be the best in the world."
Farah proved his calibre by becoming only the seventh man in history to win both the 5,000m and 10,000m at a single Olympic Games.
He hopes to achieve more success in both events, too, and will compete in August's World Athletics Championships, which are being held in Moscow.