The United States is imposing wide-ranging restrictions on economic and security assistance to Ethiopia over the conflict in the Tigray region.
Mr Blinken stressed that international action was needed to help resolve the crisis and said those involved had taken no meaningful steps to end hostilities.
Thousands of people have been killed and many more displaced since the conflict began six months ago.
All sides have been accused of numerous human rights abuses.
Britain’s Telegraph newspaper reported that several people had suffered horrific burns consistent with the use of white phosphorous. The chemical can be used legally on a battlefield but its use against civilians is considered a war crime.
Ethiopia’s foreign ministry described the allegation that chemical weapons had been used against the people of Tigray as malicious and beyond irresponsible.