A screengrab from footage aired by Iran's Fars news agency shows Hezbollah terrorists fighting in Syria. (Screengrab: Fars)

(CNSNews.com) – The governments of Israel and Jordan have – separately – both voiced concern about the growing influence of Iran on their doorsteps, at a time when security experts warn that the defeat of ISIS could usher a dangerous new regional threat as Iran and its allies move into the vacuum left by the retreating Sunni terrorists.

The chief of the Mossad intelligence agency early this week briefed Israel’s cabinet about Iran’s expanding influence through proxies in Syria, Lebanon, Iraq and Yemen, an evaluation summarized by Prime Minister Binyamin Netanyahu as “ISIS out, Iran in.”

“Our policy is clear,” Netanyahu told a meeting in the coastal city of Ashdod after receiving the intelligence review from Mossad head Yossi Cohen.

“We strongly oppose the military buildup of Iran and its proxies, first and foremost Hezbollah in Syria, and we will do everything necessary to maintain Israel’s security.”

Cohen told the cabinet that Tehran, both directly and through its proxies, was “working to fill the void” in the region, left as ISIS loses territory in Syria and Iraq.

He also said the Iranian economy has been strengthened as a result of the Joint Comprehensive Plan of Action (JCPOA) reached in 2015, which netted Iran sanctions relief in return for limitations on its nuclear program.

Iran is deeply involved in the Syrian civil war, fighting alongside its longstanding Lebanese proxy Hezbollah and Shi’ite militias from Iraq, Pakistan, Afghanistan, and elsewhere to prop up President Bashar al-Assad’s regime.

Assad loyalists and Iranian-backed Shi’ite allies recently returned to a section of the Syria-Jordan border that had formerly been held by what the army identified as ISIS jihadists.

The Syrian military announced last Thursday that it had recaptured security points along a 30 kilometer stretch of the border, “after inflicting heavy losses upon ISIS terrorists in personnel and weaponry.

A truce has been holding, with some violations, in southern Syria since early July, under an agreement reached by the U.S., Russia and Jordan. Israel is believed to be worried that the arrangement is paving the way for an expanded Iranian influence in the area.

Cohen and other senior security officials are heading for Washington this week for talks with Trump administration security officials, expected to focus on Israeli concerns about the situation in Syria and Lebanon.

A Jordanian government spokesman this week also expressed concern about the presence of pro-Assad sectarian militias near the Syria-Jordan border.

Jordanian media quoted Mohammad Moumani, minister of state for media affairs, as saying the kingdom will not allow such groups to have a foothold near its territory, views the development as a “strategic threat” and will “take the necessary measures to ensure there is security and stability on our border.”

Moumani also said that the international community and “world powers” regard the situation as seriously as Jordan does, and that some “regional countries” take it even more seriously than Jordan does – possibly a reference to Israel and Saudi Arabia, Iran’s main regional rivals.

In a column for Al-Hurra Digital on Monday, Ilan Berman, senior vice-president of the American Foreign Policy Council, reported that the size of Shi’ite militias mobilized by Iran over the past two years has been estimated at upwards of 50,000, an even greater number than that of foreign Sunni extremists who flocked to the region to fight for the ISIS “caliphate.”

Berman said the Shi’ite force “represents a grave and growing threat to the Middle East.”

“And in the future, Iran's leaders may well harness their new expeditionary force beyond the Syrian battlefield, using it as a tool to pursue other geopolitical objectives and target regional rivals,” he wrote.

“If they do, the nations of the Middle East will be faced with a new, and formidable, asymmetric adversary. So, too, will the United States.”