The Iran nuclear crisis is far from over, but Tehran appears to have made a subtle blink -- backing away from its threat a few weeks ago to close the Strait of Hormuz in response to escalating U.S. sanctions.

The softening of Iran's position followed a warning by a U.S. emissary this month that any effort to close the strait would trigger a potentially devastating U.S. response. Clearly, Tehran got the message -- with a top Iranian official Thursday publicly disavowing the earlier saber-rattling.

What started the jitters was a bellicose statement in late December by Vice President Mohammad Reza Rahimi that Iran would close the strait if the West imposed new sanctions on Iranian oil. On Jan. 3, a senior Iranian admiral said his country's navy had practiced closing the strait; he warned that the aircraft carrier USS John C. Stennis, which recently departed the gulf, should not return. But U.S. intelligence quickly picked up signs that some Iranian leaders were unhappy with the blustering comments.

The foreign minister's statement, taken with other developments, suggests that the war fever of recent weeks may be ebbing. There's no progress yet on the core issue of Iran's nuclear program, but the United States has clarified its "red lines" in the crisis, and Iran has indicated by its public response that it understands. The American back channel to Iran is an intriguing new factor. U.S. officials wouldn't disclose the identity of the emissary, but they said the person delivered an oral briefing that included both the warning on the strait and the reiteration of U.S. interest in serious negotiations.

The private message is said to have been similar to a public version offered by White House spokesman Tommy Vietor: "The United States and the international community have a strong interest in the free flow of commerce and freedom of navigation in all international waterways. Since taking office, the president has made it clear that he is willing to engage constructively and seriously with Iran about its nuclear program."

It's possible that Iran's recent statements -- both hawkish and dovish -- are responses to economic sanctions that are beginning to have a serious impact. Iran's biggest customers -- including China and India -- are beginning to reduce their oil purchases, and looking to Saudi Arabia to make up the difference.

This squeeze has begun to produce a financial run at home, as Iranians scramble for dollars that are in short supply. According to the New York Times, the Iranian currency fell to its lowest level ever against the dollar on Wednesday.

Putting these elements together, one intelligence official explained: "Iran is deterred now from crossing the Rubicon and developing nuclear weapons." This official says Iran wants all the necessary components of a nuclear weapon -- but wait to cross the threshold.

What the Obama administration wants are safeguards that, while allowing Iran to have a civilian nuclear program, prevent weaponization. President Obama summed up his goal in an interview with Time's Fareed Zakaria: "The Iranians have a very clear path where they say, we're not going to produce weapons, we won't stockpile material that can be used for weapons. The international community then says, we will work with you to develop your peaceful nuclear energy capacity, subject to the kinds of inspections that other countries have agreed to in the past."

This confrontation still has a long way to run. But last week's exchanges made clear, at least, that urgent messages are being sent and received between Washington and Tehran.