NAHR AL-BARED, Lebanon - The United States sent more ammunition on Saturday to Lebanon whose army is struggling to defeat a group of heavily armed Islamist militants holed up inside a Palestinian refugee camp.Three US Air Force cargo planes landed at BeirutÂ’s airport and unloaded ammunition and other equipment bound for the army, airport sources said. Six planes carrying similar military aid from the US and Arab allies had arrived on Friday. The shipments, promised months ago but rushed after fighting erupted between the army and Fatah al-Islam militants on May 20, arrived as Lebanese soldiers beefed up their positions around Nahr al-Bared camp, the main base for the militants.