The US tried and failed to pressure Iraq, Turkey and Pakistan to close their borders with Iran.
The first step in the campaign of the United States to economically strangle Iran was a naval blockade of its ports, while cutting off Iranian trade by sea. This was followed by a series of new sanctions, which grounded a large part of the country's air transport network.
Now, the United States is going after Iran's last economic artery: its land routes. Only there, Washington ran into a problem.
For weeks, U.S. officials have tried — and failed — to diplomatically pressure Iran's neighbors to close their border crossings, according to three Iraqi officials and one U.S. official familiar with the talks, who requested anonymity to speak candidly.
These neighboring countries, mainly Turkey, Iraq and Pakistan, are increasingly wary and resentful of American policies that they say could harm them as well as Tehran.
Many of those countries were already frustrated with Washington for ignoring their pleas not to start a war with Israel against Iran in February, a conflict in which they suffered economic costs and physical destruction.
So, on Saturday, the US military joined the effort, announcing the task force's Iron Gate, which it said would work to "prevent the movement of advanced weapons systems, dual-use technologies, approved materials and illicit revenue streams across Iran's land borders and the Caspian Sea."
It is unclear how the task force will actually operate, and it is unusual that such an economic and security campaign is being led by the US Central Command, known as CENTCOM, which oversees military operations in the Middle East.
Former US military officials and analysts say the move is likely intended to take advantage of CENTCOM's intelligence capabilities and resources, which were already focused on Iran during the war.