US Secretary of State John Kerry has said that new evidence has tested positive for use of sarin gas in the Syrian chemical attacks, Reuters reports, citing US broadcaster CNN.
He also voiced confidence that Congress "will do the right thing" on President Obama's request for approval of a unilateral military strike against the Syrian regime.
More top news
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.