The largest bloc in the Iraqi parliament, led by Shiite cleric Moqtada Al Sadr, said it will boycott the session called to elect the country's president.
Hassan Al Izari, the 73-member bloc's parliamentary chief, told a news conference on Saturday that they would not attend the session on Monday, making a vote by the 329-member house unlikely although technically a quorum could be reached.
The vote for president, a largely ceremonial role traditionally reserved for Iraq's Kurds in post-Saddam Iraq, primarily pits the incumbent Barham Salih against his top challenger, former minister Hoshyar Zebari, a candidate of the Kurdistan Democratic Party (KDP).
The latter's candidacy has stirred controversy because of years-old corruption accusations against him in court that led to his dismissal from the post of finance minister in 2016.
"Our withdrawal is a message to the Kurds, in particular to the KDP, for them to agree on a single candidate," a Sadrist MP told AFP.
The MP, whose bloc's triumph in general elections last year has left Mr Al Sadr in the driving seat in complex negotiations to select a new prime minister, said Mr Zebari was "not a consensus [candidate]".
After having served for a decade as foreign minister followed by two years as finance minister, parliament fired Mr Zebari in September 2016, notably over charges that $1.8 million of public funds were diverted to pay for airline tickets for his personal security detail.
Mr Zebari has denied any corruption accusations.
"I have not been convicted in any court," he said in a television interview on Friday night as the charges resurfaced alongside forecasts he would unseat Mr Salih, candidate of KDP's rival in Iraqi Kurdistan, the Patriotic Union of Kurdistan (PUK).
Lahib Higel, a senior Iraq analyst at the Crisis Group, said the boycott was an attempt by Mr Al Sadr to pre-empt the Coordination Framework in breaking quorum for the presidential vote, and indicated that "perhaps a consensus government is under way after all'.
"Rather than interpreting Sadr as inconsistent, he seems to be reading the playing field. So far, Sadr has made all the tactical wins over his rivals in the Shiite Co-ordination Framework. Why risking his first loss with a lack of quorum?" she wrote on Twitter.