U.N. Secretary-General Antonio Guterres has proposed the creation of a new international monitoring force of up to several thousand personnel to take over key responsibilities following the planned withdrawal of the United Nations Interim Force in Lebanon (UNIFIL) at the end of this year, according to a letter sent to the U.N. Security Council.

The proposal comes at a sensitive moment as U.S.-mediated talks between Lebanon and Israel continue over security arrangements along their shared border, including mechanisms aimed at preventing renewed conflict and stabilizing southern Lebanon.

In a letter addressed to the Security Council’s president for the month, Colombian Ambassador Leonor Zalabata Torres, Guterres outlined what he described as options for implementing U.N. Security Council Resolution 1701 after UNIFIL's departure. The proposals were submitted in accordance with Resolution 2790 and include measures to support security and monitoring along the Blue Line, the U.N.-demarcated boundary between Lebanon and Israel, as well as assistance for the deployment of the Lebanese Armed Forces south of the Litani River.

Guterres argued that once UNIFIL’s mandate expires at the end of 2026, a new U.N. presence would be needed to facilitate de-escalation, dialogue, coordination, and liaison efforts, while supporting the Lebanese military and complementing the work of the Office of the U.N. Special Coordinator for Lebanon.

He said the ultimate objective would be to help create the conditions for a long-term resolution of the conflict between Lebanon and Israel.

The secretary-general also emphasized that the United Nations would continue to play a critical role as the temporary authority responsible for the Blue Line, maintaining a neutral role in monitoring, reporting, mapping, surveying, marking, and carrying out technical deconfliction efforts along the frontier.

The proposal comes as diplomatic efforts intensify under the administration of U.S. President Donald Trump, which has been sponsoring talks between Lebanese and Israeli officials aimed at reaching new security arrangements and preventing further escalation along the border. Those discussions also include U.S.-backed security guarantees.

Three Proposed Force Structures

Guterres presented three possible models for a future U.N. military presence in Lebanon, varying in size and capabilities.

The first and largest option would deploy 350 unarmed U.N. military observers supported by a protection force consisting of four infantry battalions of 750 armed personnel each, along with a reserve force of 700 troops. According to Guterres, this structure would provide the most credible monitoring capability along the Blue Line and up to the Litani River.

The total force under this option would number approximately 5,525 personnel, including observers, armed units, support elements, and other staff.

A second option would involve 285 unarmed military observers protected by two infantry battalions of 750 soldiers each and a reserve force of 450 personnel. Concentrated primarily in the area between the Litani River and the Blue Line, the force would monitor portions of the frontier through a combination of fixed observation posts and patrols.

That option would require roughly 3,370 personnel.

The third and smallest proposal would consist of 215 unarmed military observers, two light infantry battalions of 450 armed troops each, and a rapid reaction force of 350 personnel tasked with force protection.

Under this arrangement, the mission would monitor developments along the Blue Line and several kilometers north of it through both fixed positions and mobile observation operations.

However, Guterres acknowledged that without advanced technological capabilities, the force would not be able to maintain continuous surveillance of the entire Blue Line. He said it would nevertheless retain some ability to verify and investigate violations of Resolution 1701 as far north as the Litani River.

The total size of the force under the third option would be approximately 1,980 personnel.

Guterres stressed that any post-UNIFIL arrangement would need to include adequate protection and logistical support for unarmed military observers from the United Nations Truce Supervision Organization (UNTSO), who operate within Observer Group Lebanon.

The secretary-general also addressed broader security measures, including the international arms embargo framework affecting Lebanon and the future role of the U.N. Maritime Task Force.

The naval force currently assists the Lebanese Navy in monitoring the country’s territorial waters, securing its coastline, and preventing the unauthorized transfer of weapons and related equipment into Lebanon by sea.

The proposal is likely to spark debate among Security Council members and could face resistance from both the United States and Israel, as discussions continue over the future security architecture along the Lebanese-Israeli border following UNIFIL’s withdrawal.