The Lebanese Forces (LF) party said on Monday it will join a new national unity government led by Saad al-Hariri despite an unfair offer of cabinet posts, clearing the way for an agreement on a new cabinet five months after an election.
Hariri has been trying to form a government since the May parliamentary election, with rivalry between the LF and President Michel Aoun's Free Patriotic Movement (FPM) - both Christian groups - seen as the main obstacle.
A government formed on this basis would mark a political victory for Aoun, an ally of the Iran-backed Shia group Hezbollah, over the LF, which is the group's most prominent opponent in Lebanon.
Hariri said this month that the country's economic problems meant further delay could not be allowed. Lebanese politicians have warned that their country, which has the third highest level of public debt in the world, faces economic crisis.
LF leader Samir Geagea, in a televised news conference, said the ministerial portfolios offered to his party represented an "injustice" when compared with the size of its parliamentary bloc - 15 MPs - and the ministries offered to other groups.
"There is a very big injustice to the Lebanese Forces," he said. However, the party had decided to enter the government "to continue to work from inside the government to achieve our goals," he said.
Lebanese Parliament Speaker Nabih Berri earlier suggested a breakthrough could be imminent.
"In principle, something should happen today," Berri said in response to a question about the government. His comments were broadcast by Lebanese media.
Forming a government is seen as an essential first step on the long road to repairing Lebanon's heavily-indebted and stagnant economy, allowing authorities to start overdue reforms and unlock billions in donor financing.
Alain Aoun, an FPM member and member of parliament, said he expected agreement on the government on Monday or Tuesday. "We are almost there," he told Reuters via text message.
Hezbollah member Mohammad Raad, speaking in comments broadcast by Lebanese media, said: "We are in the last phase and the period of serious anticipation. We hope the formation will be soon".