By Rami Ayyub and Maya Gebeily JERUSALEM/BEIRUT, May 29 (Reuters) - Israeli forces have advanced to positions north of Lebanon's Litani River, Prime Minister Benjamin Netanyahu said on Friday, as Israel escalates attacks against Hezbollah militants after warning thousandsmore Lebanese to flee their villages. The Israeli advance came as the U.S. military hosted Israeli and Lebanese defence representatives in Washington on Friday to pursue a U.S.-brokered plan to forge peace between the two countries and disarm Iran-backed Hezbollah.