Iraq's government marked its first anniversary Wednesday in turmoil as its premier urged Kurd officials to hand over the Sunni vice president on terror charges, in a row that has raised communal tension.

Washington has urged calm, but Prime Minister Nuri al-Maliki threatened to replace ministers of the Sunni-backed Iraqiya bloc if they do not end a cabinet boycott, as Vice President Tareq al-Hashemi, holed up in the autonomous Kurdish region, rejected claims he ran a death squad.

Lawmakers are also due to consider a call from Maliki to sack Sunni Deputy Prime Minister Saleh al-Mutlak, who has decried the Shiite-led national unity government as a "dictatorship."

The crisis comes just days after US troops completed their withdrawal from the country, leaving behind what US President Barack Obama described as a "sovereign, stable, and self-reliant Iraq."

"We call for the government of the Kurdistan region to... hand over Hashemi to the justice system," Maliki told a Baghdad news conference. "We do not accept any interference in Iraqi justice."

Maliki also rejected Hashemi's calls for Arab League representatives to observe the investigation and any questioning, telling reporters: "We gave the Iraqi dictator Saddam Hussein a fair trial, and we will ensure that a fair trial will also be given to Hashemi," referring to the now-executed Saddam.

He also warned Hashemi and Mutlak's Iraqiya bloc that he would replace the group's nine cabinet ministers if they continued to boycott government sessions.

"Ministers have no right to suspend their membership in the government because they will be considered resigned," Maliki said. "In the next cabinet meeting, if they do not come back, we will appoint replacements."

He added that "if we don't succeed to reach an agreement, we will move towards forming a majority government," as opposed to the current national unity cabinet.

Iraqiya, which has not pulled out of the government, holds 82 of the 325 seats in parliament and controls nine ministerial posts. Earlier it said it was suspending its participation in the legislature.

The bloc, which garnered most of its support from the Sunni minority and emerged with the most seats in March 2010 elections, was out-manoeuvred for the premiership by Maliki who finished second in the polls.

Maliki's remarks came after he spoke by telephone to US Vice President Joe Biden, who urged him to work with other parties to resolve the worsening crisis that threatens Iraq's fragile political truce.

Biden spoke with Maliki and parliament speaker Osama al-Nujaifi, and "stressed the urgent need for the prime minister and the leaders of the other major blocs to meet and work through their differences together," the White House said.

Nujaifi, also a Sunni and a member of Iraqiya, said in a statement that Biden had told him that "some people are trying to trigger sectarian violence one day after the US forces' withdrawal."

The speaker later met Iran's envoy to Baghdad. Washington has persistently accused Tehran of negatively influencing Iraqi politics.

US officials also confirmed that Central Intelligence Agency Director David Petraeus, the former US military commander credited with containing sectarian violence in Iraq, had visited Baghdad in recent days.

But they said it was a previously scheduled trip to Iraq and Afghanistan and that Petraeus did not have any political talks in Baghdad.

Hashemi, meanwhile, at a defiant news conference in the Kurdish regional capital Arbil denied the charges against him.

"I swear to God that I never committed a sin when it comes to Iraqi blood," he told reporters on Tuesday. "I suggest transferring the case to Kurdistan. On this basis, I will be ready to face trial."

He added that apparent confessions aired on state television linking him to attacks were "false" and "politicised." His office has complained of "intentional harassment."

Officials issued the warrant for Hashemi's arrest on Monday, after banning him from travelling overseas.

Security officials say they have detained at least 13 of the vice president's bodyguards in recent weeks, but Hashemi's office says only three have been arrested.

Maliki and other leaders have called for talks to resolve the crisis, but the premier's spokesman told AFP he would not accept any mediation over the charges against Hashemi.

"The prime minister will not compromise the blood of Iraqis, no matter what the price," Ali Mussawi said.

Maliki has also called for Deputy Prime Minister Saleh al-Mutlak, like Hashemi a Sunni Arab and a member of the Iraqiya bloc, to be sacked after Mutlak said the premier was "worse than Saddam Hussein."

Lawmakers are due to consider Maliki's request to fire Mutlak on January 3.

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