The announcement by the US that it was suspending visa services, was met with a swift response from Turkey which matched the measures almost word-for-word. It came after Turkey's arrest of a US consulate worker, who the ambassador says was just doing his job, but who Turkey claims is being investigated for links to terrorism. This dispute represents a new low in an alliance that's been under increasing strain for the past year. The Turkish prime minister says the crisis needs to be resolved immediately. But how?