The Obama administration will announce as early as Thursday its plan to introduce new visa requirements for European travelers who are dual nationals of Iran, Iraq, Sudan or Syria, or who have visited any of these countries in the last five years.
U.S. officials and congressional aides involved in discussions say the Homeland Security Department will outline how it will phase in the new rule, designed to make it harder for Europeans who have fought for the Islamic State group to enter the United States.
The law passed by Congress in December only affects a minority of Europeans, but it has prompted great concern in countries whose citizens generally enjoy visa-free travel to the United States.
And it has drawn Iranian charges that the U.S. is violating last summer's nuclear accord by penalizing legitimate business travel to the Islamic Republic.
Iraq, Syria targeted
Iraq and Syria were targeted specifically because the Islamic State has seized significant territory in each country for its would-be caliphate. Iran and Sudan, like Syria, are designated by the U.S. as state sponsors of terrorism.
The officials and aides weren't authorized to speak publicly on the matter and demanded anonymity.
The biggest question mark concerns groups of individuals that could be exempted from the law, allowing them to continue traveling to the U.S. under the Visa Waiver Program.
According to a congressional aide, the administration will create exceptions for those who traveled to any of the four countries for government or United Nations work, or for humanitarian or journalistic reasons. Legitimate business with Iran also wouldn't be punished.
No waivers appear to apply to dual nationals.
Administration officials wouldn't comment.
It's unclear if such carve-outs would be supported by Congress; Republican aides say the bipartisan legislation wasn't intended to provide such wide discretion to the executive branch. President Barack Obama signed the bill into law in December.