Nasrallah said Hezbollah and its Shia and Christian allies no longer demanded veto power in Siniora's government but the only way out of the crisis was through a referendum to resolve the deadlock or early elections - a proposal that the prime minister and his allies have rejected.
Otherwise, he said, the opposition was willing to bide its time until circumstances become convenient for a solution or regular elections are held in 2009.
Saudi-backed talks last month between the majority and the opposition failed to resolve the five-month-old standoff.
Lebanon has been experiencing political stalemate since six opposition ministers, including all Shias, resigned from the government in November because of Siniora's refusal to give them 11 seats in the 30-member cabinet and in effect hand veto power to his opponents.
"We in the opposition became like beggars ... I don't want this 19-11 [formula] any more," Nasrallah said, closing the door for any negotiations with the majority.
"Today, the courageous decision is to return to the will of the Lebanese people."
Ten people have been killed in violent clashes since the opposition took to the streets shortly after the resignations.
Hezbollah, believed to be supported by Syria and Iran, is the most powerful group in the opposition.
The parliamentary majority is led by the Sunni, Saad al-Hariri, son of the late prime minister, Rafik al-Hariri, who was assassinated in 2005.
Nasrallah criticised the majority for asking the UN Security Council to set up an international court to try suspects in the killing of al-Hariri despite opposition demands that its laws be amended and passed by parliament.