Iran's vague threat against a U.S. aircraft carrier seems pretty empty, coming as it does after the ship already left the Persian Gulf, but it's the most aggressive language yet from the increasingly isolated republic. Ataollah Salehi, the chief of Iran's army, said, "I advise, recommend and warn them (the Americans) over the return of this carrier to the Persian Gulf because we are not in the habit of warning more than once," according to MSNBC, which quoted him via the semi-official Fars news agency. The escalated rhetoric comes as Iran's currency fell to a record low against the U.S. dollar as U.S. and E.U. sanctions over Iran's nuclear program make it harder for the country to sell its oil. The financial site Zero Hedge reported on Tuesday that oil prices were spiking "as the market is finally realizing that the escalation in the Persian Gulf is more than just for show." But while Iran's rhetoric sounds aggressive, it's worth noting that it happened after the U.S. removed its aircraft carrier, not in anticipation of any planned U.S. action. But as MSNBC reminds us, "the United States and Israel have not ruled out military action against Iran if diplomacy fails to resolve the Islamic state's nuclear row with the West." And "The U.S. Fifth Fleet, which is based in Bahrain, said it would not allow shipping to be disrupted in the [Hormuz] strait." The threat from Tehran certainly won't do anything to ease those tensions.

Update (12:06 p.m. EST): The United States has responded with a terse statement saying, "the deployment of U.S. military assets in the Persian Gulf region will continue as it has for decades." It said the carrier's departure from the Gulf was part of "regularly scheduled movements in accordance with our longstanding commitments to the security and stability of the region and in support of ongoing operations," and that "our transits of the Strait of Hormuz continue to be in compliance with international law, which guarantees our vessels the right of transit passage."