WASHINGTON, July 6 (Reuters) - U.S. Secretary of State Antony Blinken called Ethiopian Prime Minister Abiy Ahmed on Tuesday, stressing the need for all parties to commit to an immediate and indefinite ceasefire in the northern Tigray region, the State Department said. The conflict in Tigray has killed thousands of people, displaced more than 2 million and pushed hundreds of thousands to the brink of famine, with international pressure building on both sides to end hostilities. The Ethiopian government declared a unilateral ceasefire last week after its troops pulled out of the Tigray capital of Mekelle in what it called a strategic withdrawal. The Tigray People"s Liberation Front (TPLF) dismissed that truce as a joke and said it had driven the government out of the city. "That unilateral announcement needs to be followed up with concrete changes on the ground to end the conflict, to stop the atrocities and importantly to allow safe and unhindered humanitarian assistance," State Department spokesman Ned Price told reporters at a regular news briefing. Blinken also called for Abiy to commit to steps outlined by the UN Security Council last week, including the withdrawal of both Eritrean and Amhara forces from Tigray and the establishment of a process to hold those responsible for human rights abuses and atrocities accountable, Price said in a statement. Abiy"s government has been battling the TPLF since early November, when it accused the then-governing party of Tigray of attacking military bases across the region. The TPLF has denied the charges. The commander of rebel forces in Tigray on Tuesday called for a negotiated ceasefire with the Ethiopian government and a political solution to the conflict, saying the government could not win the war. read more