The election in Baghdad could take place as early as Monday, a day after parliamentary polls in autonomous Iraqi Kurdistan and one year after the Kurds' ill-fated independence referendum.

The presidency has been reserved for the Kurds since Iraq's first multi-party elections in 2005, held two years after the US-led invasion that toppled dictator Saddam Hussein.

Under a tacit accord between the Kurdistan Democratic Party (KDP) and the Patriotic Union of Kurdistan, the PUK would hold the federal presidency and the KDP the post of Iraqi Kurdistan's president.

The late Jalal Talabani served as federal president for eight years.

But the Iraqi Kurdish presidency has been left vacant since KDP leader Massud Barzani resigned at the end of his mandate in the wake of the September 2017 referendum that he championed.

The KDP and PUK candidates for president of Iraq, where the prime minister is head of government in the post-Saddam era, have been touring the south of the country to lobby support and win the backing of deputies in the federal parliament.

The PUK's Barham Saleh, a 58-year-old moderate, has served in both administrations, as Iraqi deputy premier and Kurdish prime minister.

His rival for the post of president is the KDP's Fuad Hussein, a 69-year-old former chief of staff for Barzani and veteran of the opposition to Saddam.

Unlike most Kurds, he is a Shiite, a factor likely to win support from members of the Shiite-majority parliament.

A vote is scheduled for 1700 GMT on Monday, unless the two parties unite behind a single candidate. Under the constitution, if no candidate wins a two-thirds majority, the contest can be rerun on Tuesday or at a later date.

Iraq's parliament has chosen a speaker of the house but the post of prime minister has yet to be decided, more than four months after legislative elections.

In Iraq, the speaker of parliament is always a Sunni Arab while the prime minister is Shiite and the president a Kurd.

Parliamentary coalitions -- which bring together lists of Shiites, Sunnis and Kurds -- must agree on the selection of the three positions.

Iraq's Kurds have been a key US partner in the war against the Islamic State jihadist group and had hoped their role would boost international support for statehood.

But a massive "yes" vote in the referendum for independence, deemed illegal by Iraq's federal government, backfired on the oil-rich autonomous Kurdish region.

Baghdad imposed economic penalties and sent federal troops to push Kurdish forces out of oil fields vital for the region's economy, depriving it of a key lifeline.