No matter who wins Iraqinfo-icon's electionsinfo-icon on Saturday, Iraninfo-icon is likely to maintain or even increase its sway over the country just days after Donald Trumpinfo-icon said he wanted to curtail Tehraninfo-icon's regional influence.

All five Shiainfo-icon political blocs contesting the election have, or have had, ties to Iran. The outcome will determine the extent to which Baghdadinfo-icon tilts towards Tehran at a time when Iraq is no longer so reliant on the USinfo-icon after declaring victory over Isis. 

Even if the bloc led by prime minister Haider Al-Abadi, who improved relations with the US while maintaining close ties with Iran, wins most votes he would probably need to enlist support from more staunchly pro-Iran rivals to form a government.

Mr Trump, who withdrew from a landmark nuclear deal with Iran this week, accuses Tehran of fuelling conflicts and carrying out "sinister acts" across the Middle Eastinfo-icon.

In March, US defence secretary Jim Mattis said the US had "worrisome evidence that Iran was trying to influence -- using money -- the Iraqi elections".

A western diplomat in Baghdad said Iran "funds them all [Shia groups] and has done so from post-2003. It's often small stakes, some more than others, and Tehran will use it to threaten 'if you do this you get more, if you don't you will get less'." Dhiaa al-Assadi, an MP in Shia cleric Muqtada al-Sadr's bloc, said some parties would feel beholden to Tehran if hostilities between the US and Iran escalated. Recommended Analysisinfo-icon Worldinfo-icon Paramilitary strongman sets sights on Iraq premiership "[The parties that are close to Iran] get support from Iran and ...they think they should pay back this debt to Iran, which means standing with Iran in times of distress or danger," he said.

The US-led invasion that toppled Saddam Hussein in 2003, paved the way for the Shia majority to dominate Iraqi politics, inadvertently presenting Iran with the opportunity to exert influence in a country with which it fought a brutal warinfo-icon in the 1980s. Tehran filled the gap left by the US troop withdrawal and considers Iraq its most strategic ally.  

The Shia power's regional expansion is traced to the 1979 Islamic revolutioninfo-icon, after which it sought to export its ideology and develop proxies, often aided by the activities and inaction of its rivals, analysts say. Tehran insists the Islamic republic's relations with Iraq and elsewhere are motivated by legitimate national security and foreign policyinfo-icon concerns.

In 2014, Iran was the first nation to come to Iraq's aid as Isis advanced on Baghdad. [Iran] has been able to be one step ahead of the US because Iran thinks in long-term goals rather than immediate gains, Lina Khatib, Chatham House "[Iran] has been able to be one step ahead of the US because Iran thinks in long-term goals rather than immediate gains," said Lina Khatib, at Chatham House.

"The lack of real engagement from the west has paved the way for it to increase its influence." But Ms Khatib reckoned Mr Trump's decision to withdraw from the nuclear deal could mark the "turning of the tide" and the US together with Israelinfo-icon and Saudi Arabiainfo-icon could start to counter Iran more assertively.

Saudi Arabia has also courted Baghdad in recent months. Mr Abadi's main challenge could come from a pro-Iranian alliance led by Hadi al-Ameri, who is expected to be a key powerbroker in the formation of the next government. Mr Ameri told the Financial Times he wanted to maintain ties with both Washington and Tehran but "wouldn't let anybody interfere in Iraq's affairs". He is nevertheless considered close to Qassem al-Soleimani, commander of the Quds force, the overseas wing of Iran's Revolutionary Guards.

Elements of the paramilitary forces that he led in the battle against Isis, known as Hashd, have also sent fighters to Syriainfo-icon and made threats against the US. Mr Ameri rejected concerns from some Iraqis and diplomats that Tehran wanted Hashd to evolve into a force modelled on Hizbollah or the Revolutionary Guards.

Emile Hokayem at the International Institute for Strategic Studies expected Iran to continue its regional build-up. "[Iran now has] even greater security rationale and incentives to extend its influence and networks in the region because it can foresee and wants to prepare for a potential confrontation," he said.  Israel this week launched military strikes against Iranian positions in Syria after it said Iranian forces launched rockets at the Israeli-occupied Golan Heights.  

A senior US administration official said Iran had spent more than $16bn "propping up the Assad regime and supporting its other partners and proxies in Syria, Iraq and Yemeninfo-icon" since 2012 and that it provides Hizbollah with $700m a year.