AMMAN (Reuters) - The top adviser to Iran’s supreme leader said he expects the Syrian army to soon recapture rebel-held Idlib province, as well as eastern Syria, an area where U.S.-backed militias hold swathes of territory.

Ali Akbar Velayati, Iran's Supreme Leader Ayatollah Ali Khamenei's top adviser on international affairs, in Beirut May 18, 2015. REUTERS/Mohamed Azakir

Iran is a close ally of Syrian President Bashar al-Assad and the Iranian official, Ali Akbar Velayati, was speaking in Aleppo, from which the Syrian army drove rebels after a siege last year with help from Tehran.

The military alliance backing Assad, which also includes Russia and Shi’ite Muslim militias, has this year focused on the war in central and eastern Syria against Islamic State (IS) militants.

But Damascus is now setting its sights on territory held by Kurdish-led forces backed by a U.S.-led coalition that has also been fighting the Sunni Muslim IS in northern and eastern Syria.

“Soon we will see the eastern Syria cleared, and then the Idlib area in west,” said Velayati, the top aide to Iranian Supreme Leader Ayatollah Ali Khamenei, in comments reported by Mehr news agency.

He also hailed the success of Iranian allies across the region, including Lebanon’s Hezbollah, in remarks likely to infuriate Tehran’s main regional foe Saudi Arabia, lauding a “resistance line” from Tehran to Beirut.

Assad’s forces have also made some advances into rebel-held areas in northwest Syria adjacent to Idlib, a region that represents the insurgents’ biggest remaining stronghold.

Visiting Aleppo, Velayati was quoted by a military news outlet run by Hezbollah as saying Tehran’s involvement in the Syrian civil war had averted wider violence.

“The resistance line starts from Tehran and passes through Baghdad, Damascus and Beirut to reach Palestine,” he was quoted as telling a group of Shi’ite militia volunteers by a military news outlet run by Hezbollah.

Iran’s role, first by providing military advisers and then by training and arming Shi’ite militia in support of Assad, has not only helped shape the Syrian conflict, it has strengthened Tehran’s own hand across the region.

REVOLUTIONARY THEOCRACY

For the first time, Iran’s revolutionary theocracy is exerting decisive authority in an arc of influence that Sunni Arab powers, particularly Saudi Arabia, have been warning about for years.

The Hezbollah news outlet said the fighters Velayati was addressing had come to defend the Sayeda Zeinab shrine in Damascus, a magnet for thousands of Iraqi and Afghan Shi’ite militia recruits who go there before being assigned to front lines to fight Sunni rebel groups opposed to Assad.

Almost every Shi’ite militiaman bears insignia on his combat fatigues with the words “For your sake, Sayeda Zeinab”.

Velayati’s visit was the second by a senior Iranian official to the war-torn country in nearly two weeks, showing how Tehran is openly raising its support for the Syrian government.

Iran’s military chief of staff paid a rare visit to Syria last month in which he warned Israel against breaching Syrian air space and territory a day before he visited a frontline position near Aleppo.

Saudi Arabia, its Arab allies and regional powerhouse Israel accuse Iran of seeking to expand its influence in the Arab world with the goal of carving out a land route through Iraq and Syria to the Mediterranean.

The Syrian opposition also say Shi’ite Iran’s military presence in Syria stokes sectarian conflict and blames its militias for demographic changes that have uprooted Sunnis.