Israeli and Lebanese representatives are due to meet for a fresh round of direct talks in Rome on Tuesday amid ongoing hostilities between Israel and the Iran-backed Hezbollah militia.
At the end of June, both countries agreed on a framework agreement brokered by the US that is intended to pave the way for a final peace agreement, but fighting with Hezbollah, which is not part of the talks, has continued intermittently.
Last weekend, the Israeli military carried out one of the most serious waves of attacks on Lebanon since the June ceasefire, according to Lebanese reports and eyewitnesses.
According to Lebanese security and government sources, Hezbollah's extensive tunnel system, a key component of the militia's military infrastructure, is expected to be discussed in Rome.
Retired Lebanese Brigadier General Khaled Hamadeh told dpa that the network was expanded significantly after Israel's withdrawal from southern Lebanon in 2000, when Iran increased investment in Hezbollah's military capabilities.
Israeli officials argue that the tunnels violate the spirit of the UN Security Council resolution that ended the 2006 war and calls for southern Lebanon to be free of unauthorized armed groups and weapons outside state control.
They also say Hezbollah was planning to use some tunnels near the border to infiltrate northern Israel. The claims cannot be independently verified.
The Lebanese military has increased efforts to extend state authority in southern Lebanon, dismantling weapons sites in coordination with international partners.
However, officials acknowledge that the full extent of Hezbollah's underground network remains unclear and that identifying and dismantling remaining facilities could take years.