The United Nations warned Friday that political turmoil that has repeatedly delayed efforts to change the Iraqi cabinet is a threat to the country's war against the Islamic State group.

Iraq is battling to retake more ground from IS, which seized large areas north and west of Baghdad in 2014, and Washington has also expressed concern that political disputes could distract from efforts to combat the jihadists.

Instead of voting on a new cabinet lineup, lawmakers tried to sack the parliament speaker and his deputies on Thursday, while the two previous sessions ended in a sit-in and a fistfight among MPs.

"The only party that benefits from the political divisions and chaos as well as the weakening of the state and its institutions is Daesh. We should not allow this to happen," Gyorgy Busztin, the acting head of the UN Iraq mission, said in a statement, using an Arabic acronym for IS.

"The political leaders of Iraq should place the high national interest over any other consideration and work relentlessly to ensure the political process produces solutions that would lead Iraq out of its crisis and strengthen the state and its institutions. Only through unity can Iraq win," Busztin said.

Abadi has called for the cabinet of party-affiliated ministers to be replaced by a government of technocrats, but has faced significant resistance from the powerful parties that rely on control of ministries for patronage and funds.

On Thursday, MPs voted to sack parliament speaker Salim al-Juburi and his deputies, but the speaker says the session at which the vote was held lacked a quorum and was therefore invalid.

An "emergency" session on Wednesday ended with lawmakers shouting, shoving and throwing punches in the parliament chamber, leading Juburi to call a recess.

Abadi presented a first list of cabinet nominees at the end of March, but the political blocs put forward their own candidates, and most of the premier's original list was replaced on a second presented to MPs on Tuesday.

Some MPs demanded the opportunity to vote on Abadi's original list -- from which at least two candidates had already withdrawn -- but the session was adjourned Tuesday without a vote.

Dozens of lawmakers then began a sit-in and spent the night in parliament.

Iraqi ministries have for years been shared out between powerful political parties that run them as their personal fiefdoms, relying on them for patronage and funds.

Iraqi forces have regained significant ground from IS, but the jihadists still control a large area of western Iraq and carry out frequent bombings in government-held areas.

Pentagon chief in Gulf to seek support for Iraq
Abu Dhabi (AFP) April 16, 2016 - US Defence Secretary Ashton Carter arrived in the United Arab Emirates on Saturday for a six-day Gulf tour aimed at galvanising support for Iraq as it battles the Islamic State group.

Washington is eager to see the Gulf Arab monarchies do more to help Baghdad at a crucial moment in its fight against the jihadists.

"The success of the campaign against ISIL in Iraq does depend upon political and economic progress as well," Carter said ahead of his visit, using another acronym for the jihadist group.

"It's important that we continue to support" Iraqi Prime Minister Haider al-Abadi in his efforts to build a "multisectarian" country, he said. "That's the challenge in Iraq."

Abadi is grappling with plummeting oil prices and a political crisis that led to scuffles in parliament this week, hindering his efforts to replace the cabinet.

Carter will hold talks with regional leaders including Saudi King Salman and Abu Dhabi's Crown Prince Sheikh Mohammed bin Zayed Al-Nahyan, and join US President Barack Obama at a Gulf summit in Riyadh on Thursday.

He will also meet US officials overseeing the campaign against IS.

Washington has urged its allies to increase support for the fight against the jihadists in Iraq and Syria.

Although the jihadists maintain a firm grip on vast areas of the two countries, they have suffered some serious setbacks including the loss of Ramadi in Iraq.

Retaking Iraq's second city of Mosul is among the US-led coalition's top objectives but the battle is expected to be one of the most difficult yet.

Washington says it has nearly 3,900 troops in Iraq, mostly in training and support roles.

It is said to be preparing to announce a further increase of troops, after deploying a unit specialised in ground raids to capture or kill IS leaders at the start of the year.

At a press briefing at Abu Dhabi's Al-Dhafra air base, Carter said the United States sought to further strengthen the military capabilities of the Gulf states.

"The president promised last year in Camp David that we would work very hard this year, and we have been, to identify ways that we can work better together," he said.

"They range from cyber to integrated missile defence to... special operations forces, the kinds of capabilities that they need in order to make the full contribution... to whatever happens here."