Lebanon's cabinet has given final approval to a plan for an international tribunal to try suspects in the murder of former Prime Minister Rafik Hariri.
Soldiers were deployed in central Beirut ahead of the cabinet meeting
The emergency session was held without six pro-Syrian ministers after talks to bring them back to the cabinet failed.
The pro-Western prime minister, Fouad Siniora, had offered to postpone the meeting if the ministers would return.
Tensions between the two groups were escalated by the killing on Tuesday of industry minister Pierre Gemayel.
Saturday sees the second day of a strike protesting at his killing.
Business leaders said they hoped the action would move Lebanon closer to a "national dialogue".
The cabinet approved draft United Nations plans for an international tribunal on Mr Hariri's murder earlier this month.
Before the emergency session, correspondents said that if final approval were given it would be likely to increase tensions with pro-Syrian politicians.
Rafik Hariri was killed in a massive blast in February 2005
Syria has been implicated in the bombing that killed Mr Hariri last year, but denies involvement.
After the cabinet approved the UN plan, information minister Ghazi Aridi said the move was not intended as a provocation.
"It's based on a Lebanese consensus to establish this tribunal," he said.
Mr Siniora, who called the emergency cabinet session, has been under pressure to win back the support of the pro-Syrian groups within his government.
Ministers delayed the start of the meeting by more than an hour as negotiations continued with the pro-Syrian parliamentary speaker Nabih Berri.
But it eventually went ahead without the Hezbollah movement and Mr Berri's Amal party, after they held their ground over demands for greater government representation for themselves and their allies.
Mr Berri, known as an ally of Damascus, said the emergency cabinet meeting was "unconstitutional" because it had not been approved by Lebanese President Emile Lahoud.
Allies of Damascus also say the tribunal is unconstitutional because the Shia community is no longer represented in the absence of the six pro-Syria ministers, says the BBC's Kim Ghattas in Beirut.
But other constitutional experts say the cabinet is still legal, she says.
Mr Berri's backing is essential if the tribunal is to be ratified because only the speaker can call a parliamentary session to vote on the project.
Syria has also suggested at the UN that it may not co-operate with the tribunal.
Earlier on Saturday, John Bolton, the American ambassador to the United Nations, suggested that Mr Gemayel's murder might be the "first shot" in a wider coup plot against the government.
He said recent probes into political killings in Lebanon suggested Syrian involvement.
While he did not want to pre-judge any investigation into Mr Gemayel's death, Mr Bolton said, proof of Syrian involvement would show it was "not just a supporter of terrorism but is a state actor in a terrorist fashion".
Many Lebanese accuse Damascus of orchestrating the 34-year-old's murder, although Syria explicitly denies any role.
Meanwhile, the UN Security Council has agreed to a request from the Lebanese government to help investigate Mr Gemayel's murder.
Pro-Syrian groups have already said the UN plan is illegal under Lebanon's constitution.
In 2005, Syria withdrew its troops from Lebanon after a presence of 29 years, following massive domestic and international pressure following the assassination of Hariri.