Critics of the nuclear deal with Iran want the Obama administration to quickly set firm limits on sanctions relief to prevent the international coalition that brought Tehran to the table from unraveling.

With the Joint Comprehensive Plan of Action (JCPOA) having gone into effect Oct. 18, skeptics worry that a trickle of European companies entering the Iranian market will soon turn into a flood. They say that could neuter the non-nuclear sanctions that are supposed to stay in place under the deal, while making it harder for Europe and the United States to collaborate on snapping back nuclear sanctions if Iran violates its terms.

The future of the sanctions regime "really depends on how assertive will US authorities be early on in the game, because it will set the precedent and the tone for the Europeans," said Emanuele Ottolenghi, a senior fellow at the hawkish Foundation for the Defense of Democracies who has advised Congress as well as several European foreign ministries on Iranian issues. He told Al-Monitor, "If the Europeans see that there are little consequences and there is little action against them, they’ll push the boundaries, no doubt."

US Congress has similar concerns.