BAGHDAD – Iraqi Shias, like their allies in Iran, fret that unrest in Syria could oust President Bashar al-Assad and bring to power hardline Sunnis eager to put their weight behind fellow-Sunnis in Iraq who have lost out since Saddam Hussein's fall.
They fear the turmoil next door could spill into Iraq, reignite sectarian violence and intensify a proxy battle between Iran and Saudi Arabia, which sees itself as the bastion of Sunni Islam and has never come to terms with Shia rule in Baghdad.
"If Syria falls, Iraq will work with Iran to influence events in Syria," said a senior Iraqi Shia politician, who asked not to be named.
"Change in Syria will cause major problems for Iraq. They (Sunnis) will incite the western (Sunni) part of Iraq."
Iraqi Shia militias are unlikely to fight for Assad's survival, but might respond if Sunnis in Iraq's western Anbar province were emboldened by the rise of Sunni power in Syria.
Syria was the only Arab nation to side with Iran in the 1980-88 war with Iraq. Assad's minority Alawite sect is a distant offshoot of Shia Islam. Syria links Iran logistically with its Lebanese Shia Hizbullah guerrilla protégés.
Despite violent repression that, by a UN count, has killed 2,700 people, Assad has failed to quell six months of protests mostly involving majority Sunnis. The anti-Assad movement has sought to shun any sectarian agenda, but Sunni Islamists may emerge as a significant force if the president is deposed.
"Will Iran, Hizbullah in Lebanon and their allies in Iraq stand idle and watch Assad collapse and thus bring down with him one of the pillars of the 'Shia Crescent' without reacting? Impossible," said Iraqi political analyst Ibrahim al-Sumaidaie.
"Saudi Arabia and the Sunni Arab powers will try to redraw the political map in Iraq to increase Sunni influence in decision-making because until now they have not made peace with Shia rule here," he said.
To protect their interests, Syria, Hizbullah and Iran would "try to unsettle the security situation in Iraq through their relationships with Shias and Sunnis," Sumaidaie added.
He said Iraq could provide intelligence on people and arms being smuggled across the border, and ensure ample trade and financial ties with Syria, which last week banned most imports in an effort to conserve dwindling foreign currency reserves.
Syria, which also borders Israel, Lebanon, Turkey and Jordan, has some influence in Iraq, although the two countries feuded when each was ruled by rival wings of the Baath Party.
Saddam's fall in 2003 brought majority Shias to power in Iraq, which now has better ties with Iran and Syria, allies in a regional power struggle against US-backed Sunni-ruled states.
Last year Iran brokered a deal between Iraq's main Shia factions, helping them tighten their grip on power, with the blessing of Syria and Turkey, guaranteeing another term for Prime Minister Nuri al-Maliki, a Shia, Iraqi politicians say.
Many Iraqi Shia politicians believe Saudi Arabia and other Sunni countries are scheming to topple Assad – and push Iraqi Sunnis to secede and create their own region.
"If Saudi Arabia became influential in Syria, the Wahhabis will join forces with the people in western Iraq. There will be a war inside Iraq," said the senior Shia politician.
Saudi Arabia, whose monarchy rules in a pact with ultra strict Wahhabi clerics, is at odds with Iraq's Shia-led government and intervened in Bahrain to help its Sunni rulers crush protests led by majority Shi'ites earlier this year.
Riyadh was already alarmed at popular revolts that had overthrown the US-aligned presidents of Egypt and Tunisia.
"We don't fear Sunni rule in Syria, but we fear Wahhabi influence in Syria. We have evidence that Saudi Arabia wants to break the Shia Crescent," said a Shia lawmaker.
"If a radical Sunni region was created here that wants to overthrow the Shias, everyone will fight," said the lawmaker, a member of the Badr Organization, the former armed wing of the Iranian-backed Supreme Islamic Iraqi Council.
"We have enough weapons to arm everyone."
The lawmaker ruled out military intervention in Syria by Iraqi Shia militias armed and funded by Iran. But he left the door open for an internal Iraqi sectarian conflict if the outcome of the Syrian crisis undermines Shias in Iraq.
Iraq has dozens of Sunni and Shia armed groups fighting for turf. The two best-known Shia militias, Asaib al-Haq and Kataib Hizballah, are Iranian-backed splinters from the Shia Mehdi Army of anti-US cleric Moqtada al-Sadr.
Iraqi politicians said Iran was watching Syria with alarm and would try to prevent any hardline Sunni grab for power in western Iraq, using its sway with Shias, Kurds and Sunnis.
"Iran has many good relationship with Sunni tribal sheikhs in Anbar and Salahudin provinces…to protect Shia unity and stop any plan to establish an Islamist Sunni emirate in Iraq," said the Shia lawmaker.
Another senior Shia politician close to Maliki said if Tehran loses Damascus as an ally, it would use financial aid and diplomacy to try to build up Iraq as a Shia regional power.
"Iranian clout in Iraq is stronger than any other country. Why? Because it built a relationship with the Sunnis, Shias and Kurds and it will influence the political landscape in Iraq through this," the politician said.
Since the fall of Saddam, a bitter foe of Tehran, some Sunni rulers in the Middle East have talked of the emergence of a "Shia Crescent" running from Iran through Iraq and Alawite-ruled Syria to Hizbullah-controlled Lebanon.
Iran, projecting a pan-Islamic image, rejects any such sectarian concept, referring instead to an "axis of resistance."
The Islamic Republic's influence, which has burgeoned since the US-led war in Iraq, would take a damaging hit if Assad fell, with repercussions for Iraq and the rest of the region.
Iraq is trying to end a legacy of sectarian violence that drove it to the brink of civil war in 2006-07, just as US troops prepare to complete their withdrawal by 31 December.
It has taken a muted stance on Syria, while Saudi Arabia and some other Arab nations have condemned Assad's crackdown.
Iraqi Shia politicians can give Assad diplomatic and financial support, said the senior politician, "because we don't want a government inimical to Iraq to be installed in Damascus."