When President Trump stood in the Rose Garden last May to announce the U.S. withdrawal from the Iran nuclear deal, he put 180 days on the clock for businesses worldwide to sever their ties with Tehran or else lose access to U.S. markets.

The rush for the exits began immediately, despite the efforts of politicians, particularly those in the European Union. They were unable to stop European businesses fleeing Iran despite any number of grand schemes and proclamations.

One such scheme is a tool for sanctions evasion, INSTEX, a Special Purpose Vehicle , that was announced this week in a joint statement by the French, German, and British foreign ministers. To function, INSTEX will necessarily establish an international payment system structured to avoid the U.S. financial system as a means of facilitating business between Europe and Iran. This will benefit the regime by providing economic relief and freeing up capital to fund its military and terror proxies around the globe.

The proponents of this SPV scheme are undermining U.S. sanctions against Iran and harming international security.

U.S. officials have signaled their willingness to respond, but some Europeans must believe that the administration has more bark than bite. To disabuse them, Trump should order the Treasury Department to prepare sanctions in response to INSTEX, possibly eventually sanctioning INSTEX itself, its supervisory board, or its new head Per Fischer. Trump should also consider new mechanisms to target countries working to undermine U.S. sanctions on Iran, and to remind the business community of the department’s guidance that “the provision or delivery of goods or services … to an Iranian counterparty” can result in U.S. sanctions.

The prospect of U.S. pressure affecting bilateral economic ties will make an impact on France, Germany, and the United Kingdom. The U.S. is the largest foreign investor in France and the U.K. , and the leading source of non-EU foreign investment in Germany. The French Ministry for Europe and Foreign Affairs reports that there are 4,600 subsidiaries of American companies in the country, which the U.S. says employ 481,000 people as of its last report. In Germany, there are more than 700,000 people employed by U.S. multinational enterprises, including Amazon, IBM, McDonald's, Goodyear, and GE — all of which rank among the top 50 U.S. companies in Germany . And nearly 1.4 million Brits are directly employed by U.S. companies and affiliates.

U.S. banks, too, maintain a significant presence in all three countries. BlackRock manages about €30 billion for French clients and is expanding in Paris. Morgan Stanley has plans to add to its workforce in Paris, as does Citigroup . Goldman Sachs is reportedly considering an expanded presence in Berlin for its Marcus consumer bank. J.P. Morgan is one of the leading depository/custodian banks in Germany and in the U.K. has roughly 16,000 employees . And though London has seen $1 trillion in assets leave the country post-Brexit, it remains, as of today, a major player in the financial services industry.

As for the would-be private sector leaders who would potentially make use of INSTEX, the U.S. has a long history of tracking the movement of goods as part of sanctions enforcement and could readily cut off their access to American consumers and financial markets if such activities were detected. It would, in fact, be a throwback to the type of sanctions enforcement that was dominant before former Under Secretary for Terrorism and Financial Intelligence Stuart Levey introduced the concept of restricting the movement of money rather than goods.

EU member states not involved with INSTEX and the private sector can avoid any diplomatic or economic disturbance by simply standing with the U.S. and declining to make use of it. The decision should be an easy one. Major European companies are not looking for ways to re-enter the Iranian market; therefore, INSTEX a solution to a nonexistent problem.

The administration is clearly committed to applying maximum pressure against the regime in Tehran. The establishment by European powers of a mechanism to inject foreign capital into Iran runs contrary to that commitment and will only embolden a pathologically anti-American terror state.

The U.S. must impose a cost upon any country or entity that does so — a cost that is commensurate with the danger that the terrorist regime’s malign behavior poses to international peace and security.

David Ibsen is the president of United Against Nuclear Iran.