But even that sanctions campaign hasn’t gone far enough for congressional hawks, who have now turned their focus from economic pressure to nuclear pressure.
Read: Is there still a deal to be done with Iran?
The nuclear deal allows countries to assist Iran’s civilian nuclear program. Congressional hawks now want to sanction that activity too; so far, the U.S. has been issuing sanctions waivers to allow the work to continue. Christopher Ashley Ford, the assistant secretary of state for international security and nonproliferation, said in remarks last December, “We have carefully refrained from restoring sanctions in such a way as to obstruct international cooperation with Iran [on some projects] that provide Iran opportunities to benefit from nuclear technology in ways not raising proliferation risks.” The aim, he said, was to preserve the nuclear status quo until a better deal could be negotiated.
But some hawks have argued that the waivers in effect lend international legitimacy and participation to a program they view as illegitimate. Iran itself has fueled this argument through its recent incremental violations, which some hawks see as additional proof for their view that the civilian nuclear program is really a cover for seeking nuclear weapons. “The Iranians have now changed the nuclear status quo and are trying to create a new normal of minor violations that will enable their creep toward a nuclear weapon,” the letter from Cruz, Cotton, and Rubio says. “We urge you to end these waivers.”
Mark Dubowitz, the chief executive of the Foundation for Defense of Democracies who has helped lead opposition to the Iran deal in Washington, said that measure alone would not be enough to kill the deal. He also advocates ending the waivers, but not for that reason. “I agree with my friends who say we shouldn’t be providing this, because I don’t believe we should be helping Iran develop and expand its nuclear program,” he told me. If you assume, as Dubowitz and other Iran hawks do, that Iran intends to build a nuclear weapon, then that’s reason enough to end the waivers. (Iran denies seeking to build a weapon.)
What would really kill the deal, though, would be the reimposition of United Nations sanctions that were suspended under the deal. In their letter, the senators urge Trump to seek such a “snapback” through the United Nations Security Council, arguing that under the deal’s terms, any of the original participants can seek such sanctions unilaterally. (The deal’s supporters dispute that the United States can do this, because it left the deal.)
But it may not even come to that. European countries have so far limited their response to Iran’s escalations to strongly worded statements and diplomacy, some aimed at providing Iran the economic relief it’s demanding. The statements, though, are getting stronger, and there may come a point—whether it’s Iran enriching uranium to 20 percent purity rather than the nearly 5 percent it’s now achieved, or blocking nuclear inspectors, or some other provocation European powers have not yet publicly specified—when one of the European parties seeks a snapback. They are so far extremely reluctant to take that step.