The Syrian regime is threatening to move against an antigovernment stronghold in the country’s southwest, raising pressure on Russia to keep Iran and its proxies out of a fight that could inflame tensions with Syria’s neighbor, Israel.
The Syrian military has dropped leaflets urging rebels to surrender and carried out scattered artillery attacks on their positions in the southwest province of Daraa. One of the regime’s strongest militia has been redeployed from the capital Damascus to the region, where proregime media have reported preparations for a “full-scale assault” by government forces.
Rebels say, however, that the regime is trying to pressure them into a negotiated settlement without a fight. “We haven’t seen the army amassing in the south,” said Raed Radi, a commander of a Daraa rebel group. “There is a propaganda war being waged by the regime.”
The maneuvers have cast a spotlight on a particularly complicated corner of Syria bordering both Israel and Jordan. For nearly a year, Russia, the U.S. and Jordan have backed a tenuous cease-fire that has allowed Syrian rebels to establish relative stability in the country’s southwest, stretching across the provinces of Daraa and Quneitra. Now the prospect that Iranian-backed forces, broadly present in regime-controlled areas, could join an offensive there is raising tensions with Israel and complicating Moscow’s ties with Tehran.
Russia has joined with Iran to back Syria’s President Bashar al-Assad in retaking large parts of the country, but Moscow also wants to avoid getting drawn into a fight with Israel and the U.S. The current cease-fire in the region sti[CENSORED]tes that no foreign forces should be present there.
With Islamic State nearing defeat in Syria, Israeli officials said they see a welcome and growing opportunity for Russia to push Iran out of the country entirely.
“My assessment is the Russians are interested in stabilizing their achievements in Syria, formidable achievements, and I think they too understand that if the Iranians continue on the present course, this will lead to escalation and will blow their plans out of the water,” Chagai Tzuriel, director general of Israel’s Ministry of Intelligence told reporters Monday. “I think they don’t want this either.”
In a surprise meeting with Syrian President Bashar al-Assad earlier this month, Russian President Vladimir Putin said, “It is necessary for all foreign forces to withdraw from” Syria. The comment, widely interpreted as a swipe against Iran, came as Israeli Prime Minister Benjamin Netanyahu visited Moscow earlier this month. It was echoed on Monday by Russian Foreign Minister Sergei Lavrov, who said only Syrian forces should be deployed in southern Syria.
Iran has been facing growing pressure over its presence in Syria.
Earlier this month, Israel carried out its largest-ever military operation against Iranian positions in Syria, striking dozens of Iranian military sites across the southern and central parts of the country, including targets related to logistics, intelligence and ammunition storage.
In the preceding weeks, Israel carried out other smaller strikes on Iranian military targets, having said it wouldn’t allow Tehran to entrench itself in Syria.
The U.S. has also increased pressure on Tehran, with President Donald Trump withdrawing from a nuclear deal with Iran that eased sanctions on its battered economy. This month, Secretary of State Mike Pompeo outlined 12 requirements for a new nuclear deal with Iran, including Tehran curtailing its military interventions in the Middle East and withdrawing all its forces from Syria.
On Tuesday, Mr. Netanyahu reaffirmed Israel’s position that Israel won’t allow any Iranian military entrenchment anywhere in Syria.
Russia, which directly intervened on behalf of the Assad regime in 2015, has vowed not to carry out airstrikes in support of any military offensive in the southwest. But reeling in Iran could prove challenging.
Israeli officials say there are indications Russia is prepared to compel Iranian forces, including the Iran-backed militia Hezbollah, to move back from the Israeli border with southwestern Syria.
Israel isn’t counting on that possibility alone, however. “We are acting against an Iranian military presence anywhere on Syrian territory,” Mr. Netanyahu said Tuesday. “An Iranian departure from southern Syria alone will not suffice.”
It remains unclear how much leverage Russia actually has over Iran, whether in the south or any other part of Syria. Southern rebel commanders say Iranian and other foreign Shiite militias have remained stationed in regime-held parts of Daraa province.
As the Syrian regime has emerged victorious against antigovernment rebels elsewhere in Syria, the relationship between Russia and Iran has come under strain as they pursue diverging interests. Russia’s response to Israeli strikes on Iranian targets in Syria has been muted.
The U.S., meanwhile, has expressed concern that any offensive in southwestern Syria could jeopardize stability along Jordan and Israel’s borders. On Friday, the State Department warned the U.S. “will take firm and appropriate measures in response to Assad regime violations” of the regional cease-fire, but officials haven’t said what such steps would be.
—Suha Ma’ayeh, Dov Lieber, Thomas Grove and Michael R. Gordon contributed to this article.
Write to Raja Abdulrahim at raja.abdulrahim@wsj.com and Felicia Schwartz at Felicia.Schwartz@wsj.com