Iraq's main Sunni-backed bloc on Wednesday called on Shiite Prime Minister Nuri al-Maliki to step down if he will not respect a power-sharing agreement amid a festering month-long political row.

Senior members of Iyad Allawi's Iraqiya bloc, which has largely been boycotting cabinet and parliament for the past month, also mooted the possibility of pulling out of the national unity government, but cited fears of further targeting if they went into opposition.

Ex-premier Allawi, himself a Shiite Muslim, said Maliki needed to lead a "truly participatory" government in which ministers from all factions had a say, or should step aside for another candidate or go for early elections.

He said those were the only options for resolving a political deadlock that has stoked sectarian tensions since it erupted amid the December 18 pullout of US troops from Iraq.

During a meeting of his bloc in Baghdad, Allawi said that while Iraqiya supported oft-mooted talks with its rivals, one of three things must happen if such a conference failed -- full implementation of power-sharing, a replacement for Maliki from his electoral bloc or early elections.

Iraqiya, which holds 82 seats in the 325-member parliament, has so far held back from pulling out its nine ministers from the national unity government, although they have been boycotting cabinet meetings.

The bloc won the most seats in March 2010 elections, but was out-manoeuvred by Maliki's alliance, which eventually formed the government after a prolonged impasse was finally broken in November of that year.

"The problem is that in this country ... you cannot work as an opposition because an opposition means that you are going to be accused of ... terrorism," Iraqiya Deputy Prime Minister Saleh al-Mutlak told AFP on the sidelines of the meeting.

"This is the definition of opposition unfortunately."

Mutlak said Iraqiya would not pull out of government in the short term, but added: "Maybe there will be a time when it will do it. It's a possibility."

Maliki has called for Mutlak, a Sunni, to be sacked after he called the premier a dictator "worse than Saddam Hussein."

Iraqiya spokeswoman Maysoon al-Damaluji said the bloc was "not sure what happens if we turn into the opposition ... Opposition means that we will be further targeted. Fabricated accusations will continue to go around; we will have no protection whatsoever."

The row with Maliki erupted last month when authorities charged Sunni Arab vice president and senior Iraqiya leader Tareq al-Hashemi with running a death squad and Maliki said Mutlak should be fired.

Hashemi, who denies the charges, has been holed up in the autonomous Kurdish region for the duration of the crisis, and Kurdish officials have so far declined to hand him over to Baghdad.

On Tuesday, Iraq's cabinet clamped down on boycotting ministers by decreeing they could not run their ministries while staying away from its meetings.

The United Nations and the United States have urged calm but their calls for talks involving all of Iraq's political leaders have so far gone unheeded.

Iraqiya won the largest number of seats in the last election but Allawi, a secular Shiite, was outmanoeuvred for the premiership by Maliki, who struck a deal with another faction to expand his power base.