US officials are warning airstrikes alone may not be able to stop the advance of Islamic State fighters in Syria.

Barack Obama has met military commanders to discuss the campaign against I-S in Syria and Iraq - and the President admits it remains a difficult mission.

US-led airstrikes have continued on Kobani - a town near the Turkish border.

Pentagon spokesperson, Rear Admiral John Kirby, says the reality is that IS is going to take some towns and cities: