The United States on Friday tasked a senior diplomat with reducing tensions surrounding Ethiopia's Tigray region as fears rise that the conflict will spread.

Jeffrey Feltman, a veteran US diplomat who until 2018 served in a top UN position, was named to a new role of special envoy to the Horn of Africa.

Feltman will address the Tigray conflict as well as related tensions between Ethiopia and Sudan, which has taken in refugees and sent troops into a disputed border area.

He will also take up disputes over the Grand Ethiopian Renaissance Dam, a massive project that Egypt and Sudan fear will deprive them of vital water resources.

"At a moment of profound change for this strategic region, high-level US engagement is vital to mitigate the risks posed by escalating conflict while providing support to once-in-a-generation opportunities for reform," Secretary of State Antony Blinken said in a statement.

The announcement comes a day after the UN Security Council voiced alarm over Tigray, where the UN aid chief says that people have started to die of hunger and sexual violence has been used as a weapon of war.

Blinken has previously spoken of "ethnic cleansing" in the region by troops of neighboring Eritrea, which has since announced a pullout.

Ethiopia, a US ally, launched an offensive in Tigray in November after the local ruling party was blamed for attacks on military installations.

The former administration of Donald Trump unsuccessfully sought to mediate a solution on the mega-dam at the behest of Egypt.