WASHINGTON, June 29 (Reuters) - Ethiopia and Eritrea should anticipate further actions from the United States if the announced cessation of hostilities does not lead to improvements in the Tigray region, a senior U.S. State Department official said on Tuesday. Robert 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. read more 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. "We will not stand by in the face of horrors in Tigray," he said, urging the Eritrean government to immediately join in the cessation of hostilities and calling for a commitment of all parties to a permanent, negotiated ceasefire in the region. "Every effort must be made to make this ceasefire meaningful, including discussions with all parties to the conflict," said Representative Karen Bass, who chairs the panel"s Africa subcommittee. House Foreign Affairs Committee Chairman Greg Meeks said that if the disaster in Tigray is not abated, "we could witness one of our closest and most powerful allies in Africa march toward civil war and, eventually, a state collapse." The fighting has been punctuated by reports of gang rapes and mass killings of civilians. At least 12 aid workers have been killed. read more Last week, an Ethiopian military airstrike on a crowded market killed at least 64 people and wounded 180. Doctors said that children were among the dead and wounded and that Ethiopian troops prevented ambulances from reaching the scene for more than a day. The military said all the victims were combatants. read more Representative Michael McCaul, the committee"s top Republican, said that in his assessment acts of genocide had been carried out against residents of Tigray and called for targeted sanctions. Secretary of State Antony Blinken said he raised the issue at a Group of 20 meeting of foreign ministers in Italy. "I sought robust action to push all parties to commit to a negotiated ceasefire to resolve the conflict in Tigray," he tweeted.