UN chief Ban Ki-moon was due to arrive in Lebanon on Friday after saying he hoped to see Lebanon's rival parties take "concrete steps" toward the disarmament of Hezbollah.
Ban told Arabic-language daily Al-Nahar, without naming Hezbollah specifically, that disarming the Iranian-backed Shiite militant group was necessary, as no state could function properly if it did not monopolise military power.
The UN chief, who was due in Beirut later on Friday at the start of a three-day visit, said he expected negotiations between the Hezbollah camp and the Western-backed opposition in Lebanon to eventually lead to the disarmament of all militias.
However, he told Al-Nahar that he did not expect this to happen overnight.
Hezbollah is the only Lebanese faction that refused to surrender its weapons after the 1975-1990 civil war, arguing that they were needed to defend the country against Israeli aggression.
Israel failed to cause significant damage to the group in 2006 but devastated much of Lebanon's infrastructure, killing over 1,000 Lebanese, mostly civilians. Hezbollah currently dominates the Lebanese government.