Accusing Washington of "strangling" its economy, Tehran has asked the court in The Hague to order Washington to lift the measures, reimposed after US President Donald Trump pulled out of a multilateral 2015 accord.
Despite its long enmity with the United States, Iran brought the case under a 1955 "friendship treaty" that predates the country's Islamic Revolution.
Washington has forcefully told the court, which rules on disputes between United Nations member states, that it has no jurisdiction to rule on the case as it concerns a matter of national security.
The ruling on Wednesday (Oct 3) at 0800 GMT (4pm Singapore time) - in the grand surroundings of the 1913-built Peace Palace in the Dutch city - follows four days of hearings at the end of August.
Rulings by the ICJ are binding and cannot be appealed, but it has no way to enforce its decisions.
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"If the court orders measures, they should be respected," Eric De Brabandere, a professor of international law at the University of Leiden, told AFP.
If the court decides it has jurisdiction, it will likely "declare that the parties should refrain from aggravating the dispute", but any steps beyond this remain to be seen, he said.
The 2015 nuclear deal saw Iran agree to limit its nuclear programme and let in international inspectors in return for an end to years of sanctions by the West.
But Trump pulled out of the deal in May, to the dismay of European allies, arguing that funds from the lifting of sanctions under the pact had been used to support terrorism and build nuclear-capable missiles.
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