Syria has agreed to allow a UN investigator to question members of President Bashar Assad's inner circle about the assassination in February of Lebanon's former prime minister.
UN investigator Detlev Mehlis is visiting Damascus for the first time since his team began its inquiry into the February 14 killing of former Lebanese Prime Minister Rafik Hariri in a bombing.
The United Nations has said it is giving Mr Mehlis until October 25th to complete his investigation - an extension of 40 days.
Damascus invited Mr Mehlis after he accused Syria of holding up his investigation by ignoring requests to question Syrian officials.
Mr Mehlis's push to question Mr Assad's allies turns up the pressure on Syria after the UN investigation accused four once-powerful Lebanese generals who carried out Syrian policy in Lebanon of involvement in Mr Hariri's assassination.
Syria has denied involvement in the murder. On Sunday, it promised to cooperate with the inquiry, which began June 17th.
Mr Mehlis has said there are no Syrian suspects, and those he wants to question will stand as witnesses.
Lebanese media have said those include Syria's last intelligence chief in Lebanon, two aides, and Syrian Interior Minister Ghazi Kenaan, who was intelligence chief in Lebanon until five years ago.
Syria had troops in Lebanon for 29 years and dominated the country, installing allies to implement its policies. Mr Hariri had been increasingly bucking Syria's control when an explosion ripped through his motorcade, killing him and 20 others.
The assassination prompted huge anti-Syrian demonstrations that helped force Damascus to pull out its military in April.