BEIRUT/GENEVA, March 2, 2018 (Reuters) - Syrian government forces aim to advance into the eastern Ghouta region one“bite” at a time, a pro-government commander said on Friday, as a war monitor said the army had seized new ground from rebels. In one of the deadliest offensives of the war, government air strikes and bombardment have killed hundreds of people over 12 days in eastern Ghouta, an area of besieged towns and farms that is the last major rebel-controlled area near the capital. U.S. President Donald Trump spoke to the leaders of France and Germany about the situation on Friday. France said President Emmanuel Macron and Trump agreed to work together to implement a U.N.-backed ceasefire that has failed to stop the onslaught, and called on Russia to get Damascus to abide by it. The U.N. Security Council on Saturday called for a 30-day countrywide truce. Russia, which backs the Syrian government in the war, has instead called for daily humanitarian ceasefires from 9 a.m. to 2 p.m. (0700 GMT to 1200 GMT). The U.S. State Department on Thursday dismissed Russia's humanitarian ceasefire plan as“a joke”, saying people were afraid to leave the area through a“humanitarian corridor” because of fear of conscription, exile or death. The U.N. High Commissioner for Human Rights, Zeid bin Ra'ad al-Hussein, said in an emergency meeting of the United Nations' Human Rights Council on Friday that events in eastern Ghouta likely included“war crimes and potentially crimes against humanity”. “Syria must be referred to the International Criminal Court. Attempts to thwart justice and shield these criminals are disgraceful,” he said. The war has escalated on several fronts this year, with the collapse of Islamic State giving way to other conflicts between Syrian and international parties, including Turkey which said eight more of its soldiers had been killed fighting Kurdish militias in the Afrin area of northwestern Syria.