A Treasury Department statement cited the “continued role” the Eritreans play in the war, accusing forces of "looting, sexual assault, killing civilians, and blocking humanitarian aid".
The United States has imposed sanctions on the Eritrean military and other Eritrea-based individuals and entities.
The US Treasury Department said on Friday it blacklisted Eritrea's military, its ruling political party the People’s Front for Democracy and Justice (PFDJ), the party's economic adviser and the head of the Eritrean national security office.
"We condemn the continued role played by Eritrean actors who are contributing to the violence in northern Ethiopia, which has undermined the stability and integrity of the state and resulted in a humanitarian disaster," Andrea Gacki, director of the Treasury's Office of Foreign Assets Groups, said.
The US statement noted “numerous reports of looting, sexual assault, killing civilians, and blocking humanitarian aid" by Eritrean forces.
Eritrean soldiers have disguised themselves in old Ethiopian military uniforms, blocked critical aid routes and threatened staff in a key hospital in northern Ethiopia, the statement said.
US Secretary of State Antony Blinken said in a statement that sanctions were not being imposed at this time on the Ethiopian government or the TPLF.
But he added that "if the parties fail to make meaningful progress, the United States stands ready to pursue additional sanctions, including against the Government of Ethiopia and the TPLF."
Push for a ceasefire
War broke out in November 2020 between Ethiopian federal troops and forces loyal to the Tigray People's Liberation Front (TPLF), the ruling party of Tigray.
Thousands have been killed in the conflict, which has since spread into two neighbouring regions in northern Ethiopia.
The warring parties have so far rejected calls from the United States, the United Nations and the African Union for a ceasefire. Both the government and the Tigrayan sides have set conditions that the other rejects.
US Special Envoy for the Horn of Africa Jeffrey Feltman visited the Ethiopian capital Addis Ababa this week to push for a ceasefire. He returned to Washington on Thursday to consult with Blinken, the State Department said.