The leaders gathered for the talks at parliament house in central Beirut amid tight security on Thursday, after both sides threatened on Monday to take to the streets in protest.
Sources said that majority coalition leaders would reject the proposal, put forward by Michel al-Murr, the former deputy prime minister.
The coalition is willing to bring in representatives of Michel Aoun, the Christian opposition leader and a Hezbollah ally, but not to surrender a third of seats to the opposition, they said.
Hezbollah and Amal, its main ally, have five ministers in a government of 24. Emile Lahoud, the president, has one ally in the cabinet. Opponents of Syrian influence control the other ministries.
A third of ministers plus one can block motions in cabinet and automatically bring down the government by resigning.
Hezbollah calls for change
Hezbollah, which claimed victory in its war with Israel in July and August, has led calls for a change in the government now dominated by anti-Syria politicians from the majority bloc in parliament.
Hezbollah accuses Fuad Siniora, the prime minister, of failing to back it during the war and of supporting US and Israeli demands for the disarmament of its fighters.
Hezbollah is popular with Lebanon's large Shia Muslim community. It says it will stage demonstrations to demand elections unless more of its allies are admitted to the cabinet by mid-November.
Rival demonstrations by the pro- and anti-Syrian camps would further destabilise Lebanon.
Under international pressure, Syria ended a 29-year military presence in its smaller neighbour in April last year after the killing of Rafiq al-Hariri, a former prime minister, led to mass protests against Syrian influence in the country.
Anti-Syrian politicians swept to victory in ensuing elections.