Syrian state media says government forces have captured areas near the border with Lebanon, cutting supply lines for opposition fighters.
Syrian troops are approaching the mountain resort of Zabadani, which has been under rebel control for two years.
State TV says troops in the Qalamoun region reached the edge of the Lebanese border town Tufeil.
The Britain-based Syrian Observatory for Human Rights reported clashes in the area on Friday.
Syrian forces, bolstered by fighters from the Lebanese Shiite militant group Hezbollah, have systematically captured most of the rebel-held towns along the mountainous frontier since launching an offensive in the region in November.
Syria's conflict, now in its fourth year, has killed at least 160,000 people, according to activists.