A report in March on UNDOF activities said Syria's armed forces maintained positions in the Golan which violated the accord, as did Israel's deployment to the area of 155 mm artillery, Iron Dome anti-missile systems and related equipment.
The southwest was an early hotbed of the uprising against Syrian President Bashar Assad and defeat there stands to leave rebels with just one remaining stronghold - the area around Idlib province bordering Turkey in the northwest.
"The forces deployed this morning as part of preparations and readiness in light of developments on the Syrian Golan Heights", the military said on Twitter, adding that Israel was holding to a policy of non-intervention in Syria's civil war.
This photo provided by Nabaa Media, a Syrian opposition media outlet, shows smoke rising over buildings hit by a Syrian government forces bombardment in Daraa, southern Syria, on Thursday.
Talks had collapsed on Saturday as pro-Syrian government forces, backed by Russian air power, took a string of towns and villages in their fresh offensive against rebel-held areas of Syria's south.
According to a war monitoring group, the offensive has uprooted more than 120,000 civilians, driving majority towards the border with Jordan and the Israeli-occupied Golan Heights.
The massing refugees at the border aren't going to be allowed across, however. The northwestern chunk of Daraa province remains in opposition hands.
Southwest Syria is a "de-escalation zone" of reduced warfare and bombardment agreed by Russia, Jordan and the United States past year. "It's inadmissible", a negotiator in the rebel-held part of Deraa city told Agence France-Presse.
In Washington, a State Department official said the United States could not confirm the truce report, and the situation in southern Syria remained "grim" with Russian Federation and Syrian government forces continuing to bomb the area.
"[He] calls on all parties to respect their obligations under global humanitarian law and human rights law, protect civilians and facilitate safe, unimpeded and sustained humanitarian access".
The stream of refugees fleeing the battlegrounds in southern Syria towards the borders with Jordan and Israel swelled last weekend, as their number grew to 160,000, according to the UN.
Internally displaced people from Daraa province arrive near the Israeli-occupied Golan Heights in Quneitra, Syria, on Friday.
The army's offensive follows the capitulation of rebel enclaves near Homs and Damascus, including eastern Ghouta, which was recaptured after a scorched-earth assault that killed over a thousand civilians and laid waste to several towns. The Observatory says more than 100 civilians have been killed since an escalation in fighting on June 19.
With the "reconciliation" deals in Daraa, the regime has further chipped away at a U-shaped patch of territory controlled by the rebels in southern Syria.