The destruction of this caliphate must come from a Muslim-led force.
Iraq is rapidly spiralling into an unprecedented situation - and the international community is standing by.
Last summer's defeat over Syria has made the PM wary of intervention.
The pair met for 25 minutes at the White House and discussed issues including the economy, climate change and the Scottish referendum.
What tips can David Cameron learn from the annual Twiplomacy report, which studies how world leaders use Twitter? He needs a little help – not only because he's regularly insulted online, but because Barack Obama won't follow him back.
Clinton gets Obama’s donors and operatives, and in return Obama gets the Democratic nominee best able to make sure his accomplishments outlive his administration. What’s not to like?
US president says he wants the UK to remain "united" and that "it looks like things have worked pretty well".
Cameron won't repeat Romney's gaffes and enjoys the advantage of incumbency.
The man who masterminded Obama's two election victories embodies daring politics.
Former senior Obama adviser joins the party's general election team.