The Syrian army is bolstering its anti-air defenses along the border with Israel, a commander serving in the military alliance supporting the regime of Syrian President Bashar Assad said on Tuesday.

According to the Walla news website, the source said additional anti-aircraft batteries will be deployed on the Syrian Golan Heights in the coming days.

The commander, who is not a Syrian national, added that using the Russian-made Pantsir missile system would bolster anti-aircraft fortifications against Israeli warplanes.

For the past several weeks, the Assad regime has been preparing for an offensive in the Quneitra and Daraa districts in southwest Syria, near the borders with Jordan and Israel, where insurgents still hold the remaining vestiges of rebel territory in the war-torn country.

The area is part of the “de-escalation zone” delineated last year by the United States and Russia. Washington has threatened to respond harshly if Assad’s military launches an attack in the area.

According to the Assad-allied commander, the preparations for the offensive have been completed, but the regime’s forces are presently focusing on repelling Islamic State fighters from the government-controlled enclave near the city of Suwayda, also in the southwest.

The rebels believe the U.S. and Jordanian commitment to preserving the de-escalation zone will stop Damascus from launching an operation but are still bracing for the possibility. One rebel commander in the area said the forces established a united leadership front on Tuesday.

The Syrian government has said it wants to retake the area and will allow the insurgents to either accept Damascus’s authority or leave to the country’s north. The same framework has been applied to other areas in the country.

Israel has repeatedly demanded the complete withdrawal of Iranian forces all of Syria and the from the border area in particular.

The Wall Street Journal reported over the weekend that following what appeared to be an initial withdrawal of Hezbollah and pro-Iranian militia forces from the Daraa and Quneitra districts, near the Israeli border, the fighters returned disguised in Syrian army uniforms and even brandishing Syrian flags.