You're not the first person who is asked to take one of those standard tests, such as IELTS. These days they're asking anyone whose first language is not English. It sounds so stupid to ask someone who finished BS and MS from English speaking country and have several years of professional career in the US. It sounds like they don't really look at your academic and other backgrounds when they send you that type of letter. Anyways, best and safest suggestion is to take IELTS... I have an additional question: how long does it take for the whole process these days? I had applied in last November.. I never heard from them after that. I check the status online , but it only says " in process"..