A U.N. report on the assassination of former Lebanese prime minister Rafik Hariri is to be presented to Secretary General Kofi Annan on Thursday.
A U.N. spokesman said the report is expected to be sent to the Security Council on Friday, when it will likely be made public.
The report could implicate Syria in the February attack. Syrian officials have repeatedly denied any link.
U.S. and French diplomats are preparing Security Council resolutions that would criticize Syria for interference in Lebanese affairs.
In Beirut, Lebanon's President Emile Lahoud said officials have tightened security ahead of the U.N. report, and he appealed for calm.
Mr. Hariri's killing sparked massive protests in Lebanon that forced Syria to withdraw its troops and end its nearly 30-year presence in the country.