The story: Turkey's president has suggested that a breakthrough on a controversial transit corridor in the South Caucasus may be imminent. Azerbaijan plans to build a land route to Turkey via its Nakhchivan exclave. The Zangazur Corridor has sparked tension with Iran over concerns that it may cut Iranian access to Armenia.

Recep Tayyip Erdogan’s apparent proposal is for the corridor to partly run through Iran. He has insisted that Tehran views the prospect "positively." But Iran’s response has been...