The Trump administration has discovered  too late that keeping open diplomatic channels with adversaries can be useful:
The White House secretly reached out to Iran in December to propose creating a direct channel to negotiate the release of prisoners held by each side, according to U.S. officials and people briefed about the discussions, marking the first U.S. diplomatic overture to Iran on the issue under President Donald Trump.
However, Iran didn’t respond and, despite at least three subsequent offers from Washington, so far has refused to engage with U.S. officials on the offer, according to the people briefed about the discussions. The apparent impasse leaves uncertain the fate of at least four Americans currently in Iranian detention.
One of the additional benefits of the nuclear deal that Trump and his allies so frequently disparage and want to dismantle was the establishment of regular diplomatic contacts between top American and Iranian officials for the first time in decades. Simply by virtue of having held lengthy negotiations and developing a good working relationship, top officials from both governments were able to communicate directly and constructively to resolve other disputes. The brief standoff over the detained American sailors was quickly brought to a peaceful conclusion because of these contacts, and it was also possible to secure the release of Americans wrongfully detained by the Iranian government. By shutting down those contacts and declaring its unremitting hostility to Iran at every opportunity, the Trump administration threw away a valuable means of advancing U.S. interests and aiding U.S. citizens in trouble. Now that the administration seems to sees the advantage in negotiating with Iran for something, it can’t fall back on the channels created by the diplomatic success that Trump denounces. There is always a cost to rejecting engagement, and the benefits of doing so are elusive.
Ideally, Iran would release the prisoners it has wrongfully detained without any further delay, but failing that the U.S. should be in a position where it can negotiate effectively for their release. The best way to do that short of reestablishing full, normal relations with Tehran would have been to maintain the channels that were created during the negotiations over the nuclear deal. Because Trump and his officials burned those bridges as part of their obsession with Iran, they are now finding that Iran is much less receptive to their overtures.