"The Lebanese opposition stresses its adherence to ... [firstly] agreeing on the representation [of parties] in the formation of a national unity government, and [secondly] to agree on a new electoral law," an opposition statement said.
"The agreement would be crowned by electing General Michel Suleiman [Lebanon's army chief] as president as agreed."
The two sides have agreed on Suleiman as a consensus candidate to succeed Emile Lahoud, the former pro-Syrian president, who stood down at the end of his term of office in November.
Lebanon has been without a president since as differences over the makeup of a new unity government and proposed changes to the electoral law have stalled the process.
Tareq Mitri, Lebanon's acting foreign minister, accused the Hezbollah-led opposition of showing insufficient respect for the efforts of the Qatari mediators to find a compromise.
Samir Geagea, a prominent Christian leader, said the dialogue had been dealt a "heavy blow" by the opposition, which he charged "took matters back to square one".
Qatar has also proposed including a clause in the final statement of the talks requiring all sides to denounce any new resort to armed violence in internal Lebanese disputes.
Disagreements between the two sides over Hezbollah's weapons have proved an additional stumbling block in the talks.
The government representatives insisted that it be on the agenda, but Hezbollah's delegates have made clear earlier in the week that the issue is "not up for discussion".
Attempting a compromise, Akram Shehaieb, a Druze member of parliament, said the pro-government bloc wanted to address only the issue of the weapons used "against the Lebanese people in Beirut and the mountains" in the recent clashes.
"The weaponry of the resistance is a Lebanese issue which will be debated in a [subsequent] dialogue led by the president in Lebanon," he said.
Hezbollah's weapons are a sore point in Lebanon. Most militias voluntarily disarmed after Lebanon's 1975-1990 civil war, but Hezbollah was allowed to keep its arms to fight Israel and has since built up a huge arsenal.
The Qatar-hosted talks follow an Arab-mediated deal that brought an end to a week of fighting, prompted by government moves to ban Hezbollah's private communications network.
But the talks in Doha's Sheraton hotel between Lebanon's US-backed government and the opposition have made little progress, with neither camp appeared willing to make concessions.
Amr Moussa, the Arab League chief, told reporters that the talks were "in the middle of the road" but conceded the sides were each "talking about something else".
"We are trying to get them closer to each other," Moussa said.