The US Secretary of State John Kerry travels to Egypt today, in an effort to get support from Arab states on forming a coalition to tackle Islamic State militants.

Mr Kerry will meet Arab League chief Nabil al-Arabi in Cairo on the latest leg of his Middle East tour.

He's enlisted the support of 10 Arab states so far, including Saudi Arabia and Qatar, but he's ruled out Iran joining the US-led coalition, despite the country offering to help.

Mr Kerry says it would be inappropriate for Iran to join a coalition, as the US has clashed with Iran on its nuclear programme and policy in Syria.

On Friday, the CIA said IS has as many as 30,000 fighters in Syria and Iraq.

IS controls large parts of both countries and its fighters have become notorious for their brutality, but in recent weeks they have been targeted by US air strikes.

On Wednesday, President Barack Obama unveiled plans for an expansion of the US campaign against IS.

He vowed to “hunt down terrorists who threaten our country, wherever they are.”

Meanwhile, the family of a British aid worker being held hostage by Islamic State militants have urged his captors to contact them.

The extremists have threatened to kill David Haines.

The British Foreign Office insists it's doing all it can to protect the 44-year-old, who went missing in Syria in March last year.