I'm not so sure it'll be tactical nukes.
Also, they must know that from this study that Earth-Penetrating Nuclear Weapons would not be very effective and would in any case produce huge radioactive fallouts (which, besides killing thousands of civilians, could affect American troops in the area). "Dieu se rit des hommes qui se plaignent des conséquences alors qu'ils en chérissent les causes" Jacques-Bénigne Bossuet