Israel's heavy bombing of Beirut's main access road to the north severed the last major overland route for bringing relief supplies into Lebanon, international aid agencies said Friday. «This is Lebanon's umbilical cord,» Christiane Berthiaume of the World Food Program told The Associated Press. «This (road) has been the only way for us to bring in aid.» Three bridges along the Mediterranean coast road from Arida on the northern border with Syria to the Lebanese capital were destroyed, she said. U.N. agencies have about four days' worth of relief supplies left in Lebanon, the U.N. Office for the Coordination of Humanitarian Affairs said Friday. Discussions with the Israelis about increasing the flow of aid have intensified, said Ben Negus, an OCHA official in New York. «There are not a great deal of humanitarian relief supplies left in Beirut at this moment,» he said.