US President Barack Obama discussed with British Prime Minister David Cameron, in a telephone conversation they held Thursday.One of the main topics they discussed was the Syrian crisis. The White House released a statement today saying that the two leaders discussed the humanitarian crisis in Syria and stressed their commitment to the Geneva 2 convention on Syria. Obama noted during the conversation that there was progress in the dismantling of Syrian nuclear weapons.On other issues, Obama expressed his support to Cameron's efforts in convincing leaders in Afghanistan and Pakistan to take substantial steps to establish peace and stability.