BAGHDAD — Prime Minister al-Maliki faces a revolt within his party by factions that want him out as Iraqi leader, according to officials in his office and the political party he leads.

Ibrahim al-Jaafari, Mr. Maliki’s predecessor, leads the challenge and already has approached leaders of the country’s two main Kurdish parties, Parliament’s two Sunni Arab blocs, and lawmakers loyal to powerful Shiite cleric Moqtada al-Sadr.

Mr. Jaafari’s campaign, the officials said, was based on his concerns that Mr. Maliki’s policies had led Iraq into turmoil because the prime minister was doing too little to promote national reconciliation.

The former prime minister also has approached Grand Ayatollah Ali al-Sistani, Iraq’s top Shiite cleric, proposing a “national salvation” government to replace the Maliki coalition. The Iranian-born Ayatollah Sistani refused to endorse the proposal, the officials said.

“Al-Jaafari is proposing a national and nonsectarian political plan to save the nation,” said Faleh al-Fayadh, a Dawa Party lawmaker familiar with the former prime minister’s contacts.

Other officials, however, said Mr. Jaafari had only an outside chance of replacing or ousting Mr. Maliki. But they said the challenge could undermine Mr. Maliki and further entangle efforts at meeting important legislative benchmarks sought by Washington. They spoke of the sensitive political wrangling only on condition of anonymity.

The officials would not give details of the rift between Messrs. Maliki and Jaafari, saying only that it began two months ago when a Dawa Party congress voted to replace Mr. Jaafari with Mr. Maliki as its leader.

Mr. Jaafari and other senior Dawa members are questioning the legality of that vote and the former prime minister has since boycotted all official party functions, Mr. Fayadh said.

The usually secretive Dawa, which is made up of two factions, has 25 of Parliament’s 275 seats but draws its strength from being a key faction of a large Shiite alliance. Ali al-Dabbagh, the government’s spokesman, declined to comment on the rift between Messrs. Maliki and Jaafari, arguing that it was a matter for the Dawa to deal with.

“There should be no objections for a figure like al-Jaafari to try and put together a new political bloc provided that this will be of service to the political process,” he said.