Godec, acting assistant secretary of state for the State Department's Bureau of African Affairs, said the Biden administration was far advanced in its assessment of whether to call events crimes against humanity, genocide or war crimes.
"The administration is in full agreement that horrifying atrocities are being committed in Tigray," he told the House of Representatives Foreign Affairs Committee.
The former rulers of Ethiopia's Tigray said on Monday they were back in control of the regional capital Mekelle after nearly eight months of fighting, and the government which ousted them declared an immediate unilateral ceasefire.
The developments marked a turn in a conflict that has killed thousands of people, displaced more than 2 million and pushed hundreds of thousands to the brink of famine.
Godec said Washington welcomed the Ethiopian government's decision to declare a temporary end to hostilities, but warned that the United States will watch closely to determine whether the ceasefire results in changes on the ground.