Amid heavy US pressure and fears Israel could expand its strikes on Lebanon, Prime Minister Nawaf Salam said Tuesday that the government had tasked the army with developing a plan to restrict weapons to government forces by year end.

The plan is to be presented to the government by the end of August for discussion and approval, and another cabinet session has been scheduled for Thursday to continue the talks, including on a US-proposed timetable for disarmament.

Hezbollah said the government had "committed a grave sin by taking the decision to disarm Lebanon of its weapons to resist the Israeli enemy".

The decision on the thorny issue is unprecedented since Lebanon's civil war factions gave up their weapons three and a half decades ago.

"This decision undermines Lebanon's sovereignty and gives Israel a free hand to tamper with its security, geography, politics and future existence... Therefore, we will treat this decision as if it does not exist," the Iran-backed group said in a statement.

- 'Serves Israel's interests' -

The government said its decision came as part of implementing a November ceasefire that sought to end more than a year of hostilities between Israel and Hezbollah, including two months of full-blown war.

Hezbollah said it viewed the government's move as "the result of dictates from US envoy" Tom Barrack.

It "fully serves Israel's interests and leaves Lebanon exposed to the Israeli enemy without any deterrence", the group said.

Hezbollah was the only faction that kept its weapons after Lebanon's 1975-1990 civil war.

It emerged weakened politically and militarily from its latest conflict with Israel, its arsenal pummelled and its senior leadership decimated.

Israel has kept up its strikes on Hezbollah and other targets despite the November truce, and has threatened to keep doing so until the group has been disarmed.

The group said Israel must halt those strikes before any domestic debate about its weapons and a new defence strategy can begin.

- 'Pivotal moment' -

"We are open to dialogue, ending the Israeli aggression against Lebanon, liberating its land, releasing prisoners, working to build the state, and rebuilding what was destroyed by the brutal aggression," the group said.

Hezbollah is "prepared to discuss a national security strategy", but not under Israeli fire, it added.

Two ministers affiliated with Hezbollah and its ally the Amal movement walked out of Tuesday's meeting.

Hezbollah described the walkout as "an expression of rejection" of the government's "decision to subject Lebanon to American tutelage and Israeli occupation".

The Amal movement, headed by parliament speaker Nabih Berri, accused the government of "rushing to offer more gratuitous concessions" to Israel when it should have sought to end the ongoing attacks.

It called Thursday's cabinet meeting "an opportunity for correction".

Hezbollah opponent the Lebanese Forces, one of the country's two main Christian parties, said the cabinet's decision to disarm the militant group was "a pivotal moment in Lebanon's modern history -- a long-overdue step toward restoring full state authority and sovereignty".

The Kataeb, another Christian party, called the cabinet's move "historic" and warned against "any attempt to deal with the decision negatively".

It accused the Hezbollah leader of being in denial and "trying to drag the country into a confrontation that Lebanese reject".