Prime Minister Fuad Siniora called for unity to overcome the political crisis and said the cabinet approved the document to establish the court into the murder which has been blamed on Syrian officials and their Lebanese allies.
The approval came despite a government crisis sparked by the resignation of six ministers, including two from the powerful militant group Hizbullah which accused the ruling majority of "hegemony".
"In a historic meeting, the Council of Ministers approved unanimously by those present the draft of the special tribunal," Siniora told reporters after an extraordinary cabinet session.
He said the government approval was meant "to reject and confront attempts to assassinate Lebanon... and to tell the criminals that we will not give up our right to achieve justice despite the difficulties."
"Our brothers who could not join us in taking this decision were actually with us -- in our heart, our position and our decision," Siniora said, making an appeal for unity.
Information Minister Ghazi Aridi said "this meeting is 100 percent constitutional... and the Council of Ministers will inform the United Nations" which should vote through the draft paving the way to create the court.
Reacting to the government approval, Hizbullah MP Hussein Hajj Hassan accused the ruling majority of exercising a "hegemony and monopoly on decision-making".
He told AFP that Hizbullah objected "at the way" the ruling majority had approved the UN document.
"The majority is trying to tell people that the Lebanese are in conflict over the tribunal, and this is totally untrue. We are not against the tribunal -- all Lebanese agree on this issue," Hajj Hassan said.
He said Hizbullah would only agree to return to the government if its request for a "blocking minority" share in the government is met -- a demand seen as an attempt to stymie all future government decisions.
"It cannot work without a blocking minority share. Or else there will be a big national crisis and all democratic measures are considered, including strikes and demonstrations," he said.
Environment Minister Yaacub Sarraf, close to Damascus-backed President Emile Lahoud, said earlier Monday he resigned because the cabinet had lost "constitutional legitimacy after losing the representation of a whole confession".
On Saturday, five Shia Muslim ministers quit after Siniora vowed to go ahead with the cabinet meeting to discuss the UN document for the tribunal.
The row followed the failure on Saturday of a week of national roundtable talks on forming a unity government, and after months of political stalemate because of disputes between the pro- and anti-Syrian camps in parliament.
An ongoing United Nations probe has implicated senior officials from Syria, which for decades was the power-broker in its smaller neighbour, and also Lebanese accomplices. Damascus strongly denies any connection with the Hariri killing.
Hizbullah, supported by Syria and Iran and flush from its declared "divine victory" in the summer war with Israel, had two portfolios in the 24-minister cabinet which is dominated by anti-Syrian politicians.
Two ministers from Shia ally Amal also resigned, along with Foreign Minister Fawzi Sallukh who is considered close to Hizbullah.
Siniora rejected the resignations of Sarraf, a Greek Orthodox Christian, and the five Shia ministers and invited them in a letter to return to their "effective participation" in the cabinet.
But Health Minister Mohammed Khalifeh, one of the Amal ministers who quit, said the ruling majority was free to bring "Shias not from Hizbullah or Amal" into the government.
The anti-Syrian parliamentary majority held a meeting on Sunday after which MP Saad Hariri, son of Rafiq Hariri, read a statement in their name in which Iran and Syria were accused of trying to block the court's creation.
Earlier this month, the White House sounded the alarm over what it called "mounting evidence" that Hizbullah was "preparing plans to topple" the Beirut government with the aid of its Iranian and Syrian allies.

Copyright AFP (Agence France-Presse), 2006