Lebanese President Joseph Aoun told US Secretary of State Marco Rubio on Friday that a ceasefire with Israel was crucial, as Israeli and Lebanese military delegations meet at the Pentagon. A statement from Aoun's office said that during a phone call, the president "emphasized the need to exert all efforts to reach a ceasefire, considering it an essential gateway to moving on to any other step". On the ground however, Prime Minister Benjamin Netanyahu said Friday that Israeli forces had crossed Lebanon's Litani River, which runs around 30 kilometers north of the countries' shared border. "Our forces have crossed the Litani, they have moved up to the commanding terrain. We are operating in Beirut, in the Bekaa, across the entire front and are hitting Hezbollah head on," he said during a visit to troops near the border, according to a video released by his office. Lebanese and Israeli military delegations were to hold security talks at the Pentagon on Friday, during which Beirut will demand Israel halt its attacks, which have intensified in recent days. The development comes as the United States and Hezbollah's backer Iran, were negotiating with Tehran, which insists the fighting in Lebanon must be included in any agreement ending the Middle East war. Also on Friday, the Israeli military issued evacuation warnings for seven southern Lebanese towns, two of them around 40 kilometers (25 miles) north of Israel. Lebanon's state-run National News Agency (NNA) reported several strikes across the south, and a wave of displacement as people fled the threatened towns. The attacks come a day after an Israeli strike just south of Beirut, only the second since an April 17 truce sought, unsuccessfully, to halt the fighting between Israel and Hezbollah. Lebanon's delegation includes six officers, headed by the army's director of operations, Georges Rizkallah. A Lebanese military source told AFP the delegation will "stress the need for a ceasefire, and will present the army's plan for a state weapons monopoly and the extension of state authority across the country". On the Israeli side, Brigadier General Amichai Levin, head of the strategic division within the army's planning directorate, is present in Washington for these talks, according to an Israeli military spokesman. The two countries, officially at war for decades, began direct talks in April with a fourth round expected in early June. Hezbollah's parliamentary bloc on Thursday urged Lebanese authorities to withdraw from direct negotiations with Israel, accusing Israel of "seeking to impose security coordination to benefit its aggression" in the military talks. Israel and the US want Hezbollah disarmed, a difficult task which Beirut assigned to its military last year. - Ground offensive - This week, Israel vowed to ramp up operations in Lebanon and said it was expanding ground operations in the south, which most inhabitants have fled. Residents of Marjeyoun, a Christian-majority town where some residents did not leave despite the war, received phone messages from the Israeli military on Thursday telling them not to leave the town and to avoid areas near neighboring Debbine, an AFP correspondent said. Israeli troops reached the outskirts of Debbine overnight, according to the NNA, their latest push into Lebanese territory. The correspondent saw Israeli tanks between Marjeyoun and Debbine. A ceasefire between Israel and the Iran-backed Lebanese group Hezbollah was supposed to have taken effect on April 17 but has never been observed. Both sides accuse each other of violating it and justify their attacks by the other camp's alleged breaches. Israeli attacks have killed more than 3,300 people since the start of the war on March 2, according to Lebanese authorities. UNICEF, the UN children's agency, said Friday that 15 children have been killed and 62 wounded over the past week, with 55 children killed and 212 wounded since the ceasefire announcement.