The Obama administration is reportedly using a secret channel of communication to warn Iran that closing the Straits of Hormuz, through which more than a fifth of sea-borne oil passes, is a “red line” that would provoke a response from Washington. Claiming that Iran has always kept the Straits open to international shipping, Iran allowed the USS Abraham Lincoln, on a routine visit, to pass through the Straits of Hormuz into the Persian Gulf last week.