The monthly average of such visas issued to the six countries — Iran, Libya, Somalia, Sudan, Syria and Yemen — has fallen 44 percent this year when compared with the monthly average in fiscal year 2016, according to State Department data.

The visitor visas, known as non-immigrant visas, are issued principally to business travelers, tourists and students.

Non-immigrant visas to people from all Arab nations fell 16 percent and the number issued to people from the world’s nearly 50 majority-Muslim countries fell 8 percent, even as the number issued to people from all nations was virtually unchanged.