At issue is a new law tightening visa-free travel to the US. The measure was part of a spending bill passed by Congress last week and signed by President Barack Obama.
It requires visas for citizens of Iraq, Syria, Iran and Sudan, as well as recent visitors to those countries.
Iranian leaders complained in recent days that such requirements contradict elements of the landmark nuclear deal reached this year.
In response, US Secretary of State John Kerry offered assurances that the new rules would not impact legitimate Iranian business interests and suggested they could be waived. That has led to criticism from top Republicans who say they contemplated no such waiver.