U.S. threats to impose "the toughest sanctions in history" to force Iran to buckle to its demands after nearly six months of war have raised the prospect of a new round of escalation in the Gulf. How could Iran respond to the economic pressure? Can Iran stop more oil getting out of the Middle East? Mohsen Rezaei, the former Revolutionary Guards chief and secretary of Iran's Supreme National Security Council, has already threatened to shut down oil exports — one of Tehran's main strategic approaches since the war began on February 28. "If the economic war continues, not a single drop of oil will be exported, neither through the Strait of Hormuz nor from anywhere in the Persian Gulf," he said. Iranian attacks and threats to shipping have already stopped most traffic through the Strait of Hormuz, largely shutting down a waterway that carried around a fifth of global energy before the conflict. Although some oil tankers have been moving through the strait in recent weeks, volumes remain very low and on Sunday Iran blacklisted 45 tankers it says failed to comply with the rules it wants to im