Where are Iran’s frozen assets held and how much is stuck abroad?

The United States-Iran talks in Islamabad may have already faded from the headlines, but one of the key sticking points remains – Iran’s frozen assets overseas. Tehran has been pushing for the immediate release of billions held abroad, while Washington prefers a phased approach and is not willing to unlock the funds all at once. 
This raises several questions: which countries are holding Iran’s assets, how much money is involved, why is it so critical for Tehran, and how have such funds been released in the past? We break it down in today’s Star Explains.