BAGHDAD (Reuters) - Iraqi Shi'ites, 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 Shi'ite rule in Baghdad.
"If Syria falls, Iraq will work with Iran to influence events in Syria," said a senior Iraqi Shi'ite 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 Shi'ite 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 Shi'ite Islam. Syria links Iran logistically with its Lebanese Shi'ite Hezbollah guerrilla proteges.
Despite violent repression that, by a U.N. 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, Hezbollah 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 'Shi'ite 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 Shi'ite rule here," he said.
To protect their interests, Syria, Hezbollah and Iran would "try to unsettle the security situation in Iraq through their relationships with Shi'ites and Sunnis", Sumaidaie added.
Since the fall of Saddam, a bitter foe of Tehran, some Sunni rulers in the Middle East have talked of the emergence of a "Shi'ite Crescent" running from Iran through Iraq and Alawite-ruled Syria to Hezbollah-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 U.S.-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 U.S. troops prepare to complete their withdrawal by December 31.
It has taken a muted stance on Syria, while Saudi Arabia and some other Arab nations have condemned Assad's crackdown.
Iraqi Shi'ite 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".
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 Shi'ites to power in Iraq, which now has better ties with Iran and Syria, allies in a regional power struggle against U.S.-backed Sunni-ruled states.
Last year Iran brokered a deal between Iraq's main Shi'ite 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 Shi'ite, Iraqi politicians say.
Many Iraqi Shi'ite 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 Shi'ite politician.
Saudi Arabia, whose monarchy rules in a pact with ultra strict Wahhabi clerics, is at odds with Iraq's Shi'ite-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 U.S.-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 Shi'ite Crescent," said a Shi'ite lawmaker.
"If a radical Sunni region was created here that wants to overthrow the Shi'ites, everyone will fight," said the lawmaker, a member of the Badr Organisation, 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 Shi'ite 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 Shi'ites in Iraq.
Iraq has dozens of Sunni and Shi'ite armed groups fighting for turf. The two best-known Shi'ite militias, Asaib al-Haq and Kata'ib Hizballah, are Iranian-backed splinters from the Shi'ite Mehdi Army of anti-U.S. 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 Shi'ites, Kurds and Sunnis.
"Iran has many good relationship with Sunni tribal sheikhs in Anbar and Salahudin provinces...to protect Shi'ite unity and stop any plan to establish an Islamist Sunni emirate in Iraq," said the Shi'ite lawmaker.
Another senior Shi'ite 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 Shi'ite regional power.
"Iranian clout in Iraq is stronger than any other country. Why? Because it built a relationship with the Sunnis, Shi'ites and Kurds and it will influence the political landscape in Iraq through this," the politician said.
Additional reporting by Suadad al-Salhy; Writing by Rania El Gamal; Editing by Alistair Lyon