Two UN envoys went to Damascus on Tuesday and Wednesday and held talks with Syria's deputy prime minister and foreign minister, read a brief UN statement.
"The discussions were thorough and productive and led to an agreement on the way forward," added the statement, without giving any other detail.
Ake Sellstrom, the chief inspector in the UN investigation team, and Angela Kane, the UN high representative for disarmament, were to report to UN leader Ban Ki-moon on the trip.
The UN says it has received reports of 13 attacks in the conflict.
Britain, France and the United States say all the attacks were carried out by President Bashar al-Assad's forces. Russia, Assad's main ally, says its inquiry found opposition rebels used sarin gas in Khan al-Assal.
