The Syrian army had completed preparations and was fully prepared to attack the rebel-held city of Deraa on Tuesday, as Russia announced plans to meet with the United States and Jordan.
Israel and the US have raised objections to an offensive because of the role of Iran and Iranian-backed militia groups in supporting the Syrian government and because of an existing ceasefire in the area.
The pro-Assad commander, speaking on condition of anonymity, said the Syrian army's preparations for the assault were complete. "The Syrian army will wage all the battles and has now become strong and capable," the commander said. However, a rebel commander in the Deraa region of the southwest told Reuters there was no sign of mobilisation for such an assault and accused Damascus of waging psychological warfare. Nevertheless, rebels had prepared defences, he said.
Along with Iran, Russia is also a military backer of Syrian president Bashar Al Assad. Russian foreign minister Sergei Lavrov said on Monday that only the Syrian military should be on the country's southern border.
Russia’s Deputy Foreign Minister Mikhail Bogdanov said on Tuesday that an agreement has been reached to hold a three-way meeting between the US, Russia and Jordan on the southern de-escalation zone, RIA news agency reported. It comes as Jordan said on Monday that it was talking with the US and Russia and that all three agreed on the need to preserve the de-escalation zone they brokered last year to reduce violence in the area.
Washington has warned of "firm and appropriate measures" if there are truce violations in the region.
It is expected that Russia would broker some kind of agreement between Israel and Iran over their role.
“They’re definitely looking to establish an arrangement,” said Yury Barmin, an analyst of Russian policy in the Middle East at the Russian International Affairs Council in Moscow.
Though it rarely takes credit for the strikes, Israel is believed to have struck dozens of times in Syria in recent years against Iranian military hardware in Syria and shipments of weapons intended for delivery to Hezbollah in Lebanon.
The most intense round of Israeli strikes so far took place earlier this month with a barrage of fire hitting Iranian positions as rockets fired from near the occupied Golan Heights targeted an Israeli position. Iran has admitted more than a dozen casualties amongst its ranks in Syria in recent months – thought to include a high ranking Revolutionary Guard commander - and an Israeli plane was brought down by Syrian anti-aircraft fire for the first time in decades.
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The escalation led to fears of a direct confrontation between Israel and Iran, possibly inside Syria. It has also sparked talk by analysts of a need for the two antagonists to come to a new understanding over the “rules of engagement” in their proxy conflict.
There have been reports in the past of friction between Iran and Russia in Syria, and Mr Barmin said that the Russians might also see the benefit in keeping Iran somewhat marginalised inside Syria.
“The fact that Russia allows Israel a little bit of freedom to act to side-line Iran, Israel is doing it for the Russians,” he said. “As long as the Israelis don’t threaten Assad.”
Russia also has considerations in its relationship with Iran outside Syria that would make Russia keen to avoid going too far, such as expecting a full Iranian pull-out from Syria.
It was unclear when a meeting on the issue of southern Syria might take place between the US, Jordan and Russia. But an agreement reached last year between the US, Iran, and Russia had turned the area around Deraa into a “de-escalation zone” that had successfully reduced hostilities, though was still subject to repeated violations.
Iran has provided support to the government of president Bashar Al Assad from the beginning of the conflict, while Russia’s military directly intervened in Syria in 2015, providing air power and other crucial support to the government’s forces.
Israeli defence minister Avigdor Lieberman was also expected to meet with his Russian counterpoint, Sergei Shvigo, in Moscow on Wednesday.
Mr Barmin said that Russia would have to “be creative to convince Iran that giving up on southern Syrian is not counter to Iran’s grand interest there.”
He said there was also the open question of whether Iran would accept whatever agreement Russia might broker with Israel.
Deraa has been under a years long siege, with Jordan and Israel tightly controlling their borders. One possibility is that rebels could agree to be transferred elsewhere in the county – possibly to one of the northern Syrian-provinces where rebels, largely with Turkish backing, still hold sway.
Those deals have been referred to as “forced displacement” by human rights organisations.
“I am not afraid of displacement,” said Mauwiya Al Zaabi, a 31-year-old rebel. “I’m ready to die on the land of Deraa.”
He said Iran’s support had been crucial to Mr Al Assad maintaining power in the face of widespread rebellion, whether or not they would participate in a final offensive against Deraa.
“The Iranian militia is the spearhead of the offensive of the Assad forces and its role has been clear for five years, which prevented the Syrians from their freedom and topple the regime.”