The nomination effectively guarantees Maliki, 75, the post that he last held more than a decade ago.

The shrewd politician is set to return to power today amid seismic changes in the Middle East, with Tehran's regional influence waning and tensions with Washington rising.

The Coordination Framework, an alliance of Shiite factions with varying links to Iran, said in a statement that it "decided, by majority vote, to nominate" Maliki for the position "as the candidate of the largest parliamentary bloc".

The statement spoke of Maliki's "political and administrative experience and his record in running the state".

After Iraq's November general election, the Coordination Framework, which includes Maliki, formed the majority bloc.

Soon after, it held heated talks to choose the next prime minister, along with other discussions with Sunni and Kurdish parties regarding other posts.

Iraq's parliament chose a speaker last month and should convene next to elect a new president, who will then appoint a prime minister to replace the incumbent Mohammed Shia al-Sudani.

By convention in Iraq, a Shiite Muslim holds the powerful post of prime minister, a Sunni is parliament speaker, and the largely ceremonial presidency goes to a Kurd.

Maliki, has long been a central figure in Iraq's politics and its only two-term prime minister (2006-2014) since the US invasion of 2003, which ended decades of rule by the autocratic Sunni president Saddam Hussein.

- Hard task -

Maliki, leader of the State of Law Coalition, has increased his power and influence despite his controversial past, including widespread accusations of stoking sectarian tensions, and failing to stop the Islamic State group in 2014.

He has been involved in forming alliances and his name was regularly put forward as a possible candidate for the premiership.

Seen as close to Iran, Maliki also has a record of coordinating with the US on Iraqi politics, particularly during his previous terms.

In a country that has for decades been a proxy battleground between the US and Iran, Maliki will likely face a daunting task as government formation has always been influenced by the two foes.

He will be expected to address Washington's longstanding demand that Baghdad disarm Tehran-backed factions, many of which are designated terrorist groups by the US.

Iraqi officials and diplomats told AFP last month that Washington had demanded that the eventual government exclude Iran-backed armed groups and instead move to dismantle them.

But most of these groups hold seats in parliament and have seen their political and financial clout increase.