WHEN Iranian Supreme Leader Ayatollah Ali Khamenei looks west from his Tehran residence, he can be forgiven a wry smile.

An arc of Iranian influence from the Shia republic to the shores of the Mediterranean is taking shape in the increasingly troubled and unpredictable Middle East, slowly but certainly surely.

And his great adversary in a campaign for Middle East leadership, Sunni Saudi Arabia, seems at a loss to reverse Iran’s gains.

As an unexpected bonus, President Trump’s predicted announcement recognising Jerusalem as Israel’s capital is the perfect issue for Iran and Islamist militants to use to rouse the Arabs against the US and its allies.

Tehran is building a network of proxies across the Middle East.

In Lebanon, Hezbollah, the Party of God formed with Iranian help to resist Israeli occupation of Lebanon in the early 1980s, exerts considerable political influence over the Beirut government and fields an army more powerful than the Lebanese state.

A Lebanese cabinet dominated by Hezbollah was formed last year with an ally of the group, Michel Aoun, as president. Riyadh’s attempt to force Sunni Prime Minister Saad Al-Hariri to resign last month while visiting the kingdom and his subsequent retraction when he got home demonstrate the limits of Saudi influence.

Hezbollah, the most visible Iranian proxy, has been a powerful ally to Syrian President Bashar Al-Assad in crushing opponents in the civil war. Highly-trained Hezbollah troops have supported the regime which also counts on extensive Russian military backing.

Saudi Arabia fears growing Hezbollah influence in Lebanon, not least as their fighters return from Syria, to the extent of apparently cooperating with Israel on the basis the enemy of my enemy is my friend.

Developing ties with Tel Aviv and fears there of an increasingly powerful Hezbollah on the northern border with Galilee have sparked rumours that Saudi Arabia may be offering financing for an Israeli attack on the Shia group in south Lebanon. Analysts see that as unlikely at present given the awful toll the well-equipped and battle-hardened Hezbollah fighters would impose on Israel, even if Tel Aviv eventually won, but it remains a possibility.

In war-torn Syria, Middle East analysts in Jordan and Egypt say Iranian proxies who lined up fighters were decisive in heading off the regime’s destruction. The legacy of proxies loyal to Tehran and a regime that owes its survival to Iran guarantee continued access to that key part of the arc to the Mediterranean.

Saudi efforts to support rebel groups in Syria, by contrast, have largely ended in failure or the expansion of jihadis.

Heading east to Iraq, Iran has established the 120,000-strong Popular Mobilisation Units with core personnel loyal to Tehran. The government in Baghdad of the ruling Islamic Dawa Party backs Iran as does the powerful Interior Ministry.

In Yemen, itself a tragedy on a heart-breaking scale, Shia Houthi rebels supported by Iran have given a Saudi-led alliance a bloody nose, fending off heavy bombing raids across the country with little sign of success. A missile fired recently by Houthis towards Riyadh symbolised the defiance that bombs have done little to dent.

The killing of former president Ali Abdullah Saleh by the Houthis, days after he switched allegiance to the Saudis from the Houthis, seems destined to intensify the fighting and demonstrates vividly the impotence of Riyadh.

In the kingdom itself, the major oil-producing Eastern Province where most Shia live remains a troubled area where the Saudis fear Iranian attempts to destabilise the country.

And 16 miles across a causeway over the Gulf in tiny Sunni-ruled Bahrain, riots and demonstrations in Shia villages are regular occurrences which Manama blames on Iranian agitation.

Saudi Arabia’s 32-year-old Crown Prince Mohammed Bin Salman was hailed on his appointment as a reformer, lifting a driving ban on women from next year, proposing the sale of five per cent of state oil company Aramco, and vowing to stamp out corruption.

President Trump, wowed with a glittering reception in Riyadh when he made his first foreign trip abroad after taking office, backed the young prince unequivocally and came out forcefully against Iran, setting the battle lines for a troubled Middle East.

But many analysts close to the kingdom see the prince’s plans as impetuous and over-ambitious and none have succeeded.

His Saudi-led boycott of tiny Qatar, which the kingdom assumed would quickly acquiesce in demands such as closing Al-Jazeera TV network and backing off from ties with Iran, has led to a six-month stand-off with Doha which is now supported in practical ways by Teheran and also Oman and Kuwait.

The real danger is that a cold war between Shia and Sunni that began with the Islamic revolution in Iran in 1979 turns into something much hotter. With an unpredictable Crown Prince in the kingdom and an erratic President Trump at the White House, Ali Khamenei's strategic approach to a land bridge across the Middle East looks increasingly like the winner.