UN Secretary General Kofi Annan has received the second report into the killing of former Lebanese Prime Minister Rafik Hariri.
Rafik Hariri was known for his anti-Syrian stance
The report is said to detail Syria's alleged role in the murder.
It comes days after United Nations investigator Detlev Mehlis's team questioned five Syrian officials.
Syrian President Bashar al-Assad vowed again on Sunday that he would punish any Syrian involved in the murder plot.
Damascus has strongly denied involvement in the car bomb which killed Hariri in February.
But an interim UN report in December has already implicated Syrian officials.
Most Lebanese and Syrians are now waiting anxiously to see what evidence Mr Mehlis will reveal in his second report.
The chief UN investigator has indicated it will confirm the findings of the first extensive report, but it will also include more concrete evidence.
Mr Mehlis said his investigation was not affected by the retractions of a Syrian witness two weeks ago and none of his conclusions presented to the UN Security Council in October need to be altered.
INTERIM UN FINDINGS
Assassins had considerable resources and capabilities
Evidence suggests both Syria and Lebanon were involved
Crime was prepared over several months
Hariri's movements and itineraries were monitored
Highly unlikely Syrian or Lebanese intelligence were not aware of assassination plot
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The Lebanese media have also reported that Mr Mehlis is likely to say he did not get full co-operation from Syria.
The UN has threatened unspecified action in this case and the Security Council is due to discuss the report on Tuesday. But Syrian officials insist they have co-operated fully.
"If there is a person who is involved then he must be held accountable, but at the same time to say that a Syrian person is guilty there must be evidence," Syria's President Assad said in an interview with Russia's Channel 2 television station.
And the UN investigation is by no means over, says the BBC's Kim Ghattas in the Lebanese capital, Beirut.
Lebanon has urged Mr Annan to extend Mr Mehlis's investigation by six months.
The mandate of the probe is likely to be extended for another three months, our correspondent says, even though Mr Mehlis himself will no longer lead the investigation beyond 15 December.
Hariri's murder led to widespread protests in Lebanon and extensive international pressure on Syria, forcing it to end its 29-year-old military presence in Lebanon in April.