Iran does not appear to be backing down from an increased U.S. Naval presence in their backyard, as The Washington Post reports a buildup in their "capabilities" that can threaten American vessels. The paper says that Iran is gathering an arsenal of sophisticated surface-to-ship missiles and small, speedy attack boats that could hit American warships in the Persian Gulf and the Strait of Hormuz.
While the Iranians can't hope to match the firepower of a U.S. aircraft carrier group, they can still deal a strong blow to individual ships and generally make life miserable for foreign powers trying to keep shipping lanes open. The Iranians have threatened to close the Strait in response to economic sanctions that have been imposed upon them, which has led to an increased U.S. naval presence, which has led to this Iranian buildup, which will only raise tensions even more.
The odds of the Iranians launching a preemptive assault on the Americans are still pretty low, but in every attempt by the international community to squeeze the regime in Tehran and force them to back off their nuclear program, the harder they push back. Even as their economy buckles, food prices surge, and oil exports are slashed, Iran's leaders refuse to give an inch. The nuclear program remains the one and only priority. The rest of their energy is spent reminding the Americans (and everyone else in the region) who they are dealing with.