Iraq's prime minister is due to seek parliamentary approval for a cabinet reshuffle amid mounting pressure for political reform.

A number of parliamentarians from across Iraq's political spectrum have threatened to pull out of Thursday's vote, suggesting Prime Minister Haider al-Abadi may miss the deadline set by lawmakers to submit his ministerial nominations.

The parliamentary vote comes as thousands of followers of the influential Shiite cleric Muqtada al-Sadr continue a sit-in outside the Iraqi capital's heavily fortified Green Zone, calling for political reform and an end to corruption.

In August, al-Abadi proposed a sweeping reform package to combat corruption, cut government spending and merge ministries, but his efforts have been stymied by sectarian tensions and struggles to contain the Islamic State group.