Syrian security officials say troops managed to reach the edge of the border town of Tufeil in the Qalamoun region on Friday.
Sources say the soldiers are now approaching the mountain resort of Zabadani, which has been under the control of militants for two years.
The fresh army gains technically cut supply lines for the anti-Damascus militants.
The government troops have captured most of the militant-held towns along the mountainous frontier since its November offensive began.
Over the past months, the Syrian army has achieved major victories in its battle against Takfiri groups across the country, particularly in the strategic Qalamoun region near the Lebanese border.
Syrian President Bashar al-Assad says the Takfiri war in his country has strongly shifted in favor of government forces as they have made continuous gains in their fight against the terrorists.
Syria has been gripped by deadly violence since March 2011. Over 160,000 people have reportedly been killed and millions displaced due to the violence fueled by the Western-backed militants.
The West and its regional allies including Qatar, Saudi Arabia, and Turkey are giving financial and military support to the militants.
The foreign-backed militancy in Syria has spilled over into neighboring Iraq.
Fears are growing that European militants trained and hardened in Syria may carry out terrorist attacks once they return home.
Analysts believe the Syria crisis will backfire on the West as militants are now returning to the countries they came from, including those in Europe.