WASHINGTON, July 29 (Reuters) - Washington is sending USAID Administrator Samantha Power to Ethiopia this week while warning of punitive measures if aid is unable to reach the Tigray region, where hundreds of thousands of people are believed to be experiencing famine. A statement said Power will travel to Sudan and Ethiopia from Saturday to Wednesday in a fresh diplomatic push by President Joe Biden"s administration amid fears of ethnic cleansing in the region and hopes for negotiations between the Ethiopian government and Tigrayan forces to resolve the conflict. Power is due to meet Ethiopia"s national security adviser and hopes to meet Prime Minister Abiy Ahmed, a senior USAID official said. Washington hopes she will secure unhindered humanitarian access to Tigray. "There will be I think continued punitive measures as long as we are unable to access those populations," the official said. The Ethiopian government denies blocking food aid. The Biden administration has repeatedly called for humanitarian access to Tigray. Fighting erupted there in November when the government accused the Tigray People"s Liberation Front (TPLF) of attacking military bases across the region, an accusation the group denied. The government declared victory three weeks later when it took the regional capital Mekelle, but the TPLF kept fighting and has since retaken most of Tigray. Ethiopian troops withdrew from most of Tigray in late June when the TPLF retook Mekelle. The central government declared a unilateral ceasefire on what it said were humanitarian grounds. Thousands of people have died in the fighting, around 2 million people have been displaced and more than 5 million rely on emergency food aid. Washington is also concerned about reports of mass arrests, beatings and torture of Tigrayans in custody in Addis Ababa as well as some of Abiy"s rhetoric, the official said. "The concerns that we have about ethnic cleansing and ethnic targeting are very real," the official said, adding that Power will address this in meetings with Ethiopian leadership. The Ethiopian government has denied targeting Tigrayans as an ethnic group, saying their fight is with the ruling party that controls the region. "All statements by Federal and Regional Government refer to the criminal enterprise that is TPLF and not the people of Tigray," a government-run Twitter account focused on Tigray tweeted this week.