Barack Obama has called Afghan President Hamid Karzai to detail his plans for US troops in the country.
A senior US official said the American president phoned Mr Karzai on Tuesday about his strategy to leave 9,800 troops in the country beyond 2014.
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The Labour leader did not say whether he would maintain Britain's nuclear deterrent programme.
Ukip leader Paul Nuttall also said he would want to get rid of Sharia courts.
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.