The move is "a blatant violation of the (national) pact, the constitution and Lebanese laws... and it exacerbates domestic divisions at a time when Lebanon most needs solidarity and internal unity to face Israel's aggression and preserve civil peace," Fadlallah said in a statement.
"What the enemy has been unable to do on the ground... it will not obtain in negotiations with an authority that lacks decision-making power, has abandoned its most basic duties, has failed to protect its people and cannot be trusted to safeguard national sovereignty," he added.
A statement from President Joseph Aoun's office said that a telephone call was held on Friday between the Lebanese and Israeli ambassadors to Washington and the US ambassador to Lebanon, who was also in the American city.
"During the call, it was agreed to hold the first meeting next Tuesday at the State Department to discuss declaring a ceasefire and the start date for negotiations between Lebanon and Israel under US auspices," the presidency statement said.
After a ceasefire was announced between the United States and Iran this week, the two sides have been at odds over whether it also applies to Lebanon, as Israel has kept up heavy strikes on the country and Hezbollah has responded with its own attacks.
But after Aoun's announcement, Israeli ambassador to the United States Yechiel Leiter said his country "agreed to begin formal peace negotiations" with the Lebanese government, with which it has no diplomatic relations.
A Lebanese government official told AFP on Thursday that Lebanon wants a ceasefire before starting any negotiations with Israel.
On Friday, dozens of Hezbollah supporters demonstrated outside the government headquarters and other parts of Beirut.
In tandem, Hezbollah Secretary General Naim Qassem
He emphasized that Hezbollah will not accept a return to the previous situation and called on officials to cease making "gratuitous concessions," adding that the resistance to the Israeli occupation army "will continue until the last breath."
"The enemy resorted to bloody aggression on Wednesday, but our Lebanese people are far stronger and more resilient than they believe, and the displaced have set an example of pride and morale."
Wednesday's wave of Israeli strikes on residential buildigs in Beirut and across Lebanon killed more than 300 people, and wounded hundreds.
Since the start of the escalated bombing in Lebanon on 2 March, Israeli airstrikes have killed nearly 2,000 and wounded nearly 6,500 civilians.
The death toll from nearly six weeks of war includes 248 women,165 children and 85 health workers, the Lebanese health ministry said. Nearly 100 people were killed in the past 24 hours.
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