Iran threatened to close the Strait of Hormuz if subjected to military attack or if international sanctions are imposed. According to an Iranian official, "Insecurity will spread everywhere!"
The Strait of Hormuz is the gateway connecting the Gulf region with the rest of the world. Between 20 and 30 oil tankers travel through the Strait every day, and according to the United Nations Convention on the Law of the Sea, every ship has the right of passage through the Strait as long as it doesn't pose a threat to the security or violate statutes of the coastal States.
But Iran, which is still in the process of developing a nuclear weapon, believes that it alone is entitled to the Strait, (which is named for one of its legendary leaders), and that it has the right to decide to close the Strait whenever it pleases - regardless of the interests of its Arab neighbors stretching along the other bank of the Gulf!
The Arab Gulf States, which have yet to come to an agreement with Iran over the disputed sovereignty of three Gulf islands, are signatories to international treaties [including the Law of the Sea] and are constantly striving to achieve security and stability for themselves and the region as a whole. These States cannot accept any situation in which the Strait is closed, and will never cease using all means to protect their security, stability and economic strength.
If the regime in Tehran has any doubts of the ability of the Gulf States as far as that goes, then it better read history well! Not distant history, but recent history, which dealt with a regime called the Baath regime [Iraq] - a regime that weighed heavily on Iraq's chest and represented a clear threat to its neighbors. That regime was wiped out - leaving nothing but a memory behind.