Prime Minister Nuri al-Maliki offered a general amnesty Wednesday in a rare conciliatory move to undercut support for militants whose offensive has overrun swathes of territory and threatens to tear Iraq apart.

The offer comes after a farcical opening to the new parliament, despite world leaders calling on Iraq's fractious politicians to unite urgently to help combat insurgents, as the military struggles to seize the initiative.

Maliki's surprise move, made in his weekly televised address, appeared to be a bid to split the broad alliance of jihadists, loyalists of executed dictator Saddam Hussein and anti-government tribes that has captured large chunks of five provinces, displacing hundreds of thousands of people.

"I announce the provision of amnesty for all tribes and all people who were involved in actions against the state" but who now "return to their senses," Maliki said.

But he excluded those involved in killings, and it was not immediately clear how many people might be eligible.

Analysts have said some form of political reconciliation is needed to convince Sunni Arabs angry with the Shiite-led government to turn against their co-religionists and jihadists.

The vast majority of Iraq's Sunni Arab minority do not actively support the Islamic State (IS) jihadist group spearheading the offensive, but analysts say anger over perceived mistreatment by the authorities means they are less likely to cooperate with the security forces.

- Farcical parliamentary session -

Maliki's announcement came a day after an eagerly awaited opening to the Council of Representatives descended into chaos and ended in disarray without a speaker being elected.

Washington quickly warned that "time is not on Iraq's side," with State Department spokeswoman Marie Harf calling for "extreme urgency."

UN special envoy Nickolay Mladenov said Iraqi politicians "need to realise that it is no longer business as usual."

Under a de facto agreement, the premier is a Shiite Arab, the speaker Sunni Arab and the president a Kurd.

Presiding MP Mahdi Hafez said the legislature would reconvene on July 8 if leaders were able to agree on senior posts.

In another sign of political discord, Maliki rejected Wednesday an assertion by the autonomous Kurdish region that its control of disputed territory is here to stay.

Kurdish leader Massud Barzani has even said a referendum will be held in the coming months on independence for the oil-rich region.

On the ground, Iraqi forces were struggling to break a stalemate with militants after initially wilting before the onslaught. They have since performed better, albeit with limited offensive success.

But the cost has been high. Nearly 900 security personnel were among 2,400 people killed in June, the highest figure in years, according to the United Nations.

Thousands of troops, backed by tanks, artillery and aerial cover, have made limited progress in retaking Tikrit, which fell on June 11, as a highly publicised operation appears to have hit difficulties.

- 'Advancing slowly' -

"They are advancing slowly because all of the houses and burned vehicles (en route to the city) have been rigged with explosives, and militants have deployed lots of roadside bombs and car bombs," said Ahmed Abdullah Juburi, governor of Salaheddin province of which Tikrit is the capital.

Juburi said it would be days before security forces could make a concerted push into the city.

Maliki's security spokesman also told reporters that loyalists had clashed with militants south of Baghdad.

In an effort to break the stand-off, the government has bought more than a dozen Sukhoi warplanes from Russia.

It said it aimed to begin using them in combat Wednesday, but it was unclear if that has happened.

The London-based International Institute for Strategic Studies has said three Sukhoi ground attack jets shown landing in Iraq in a video released by the defence ministry are likely from Iran, which has pledged to aid Iraq against the militants.

Loyalists are battling militants led by the IS, which Sunday declared a "caliphate," an Islamic form of government last seen under the Ottoman Empire, and ordered Muslims worldwide to pledge allegiance to their chief.

US reaches out to Saudi Arabia, Sunni, Kurd leaders in Iraq
Washington (AFP) July 02, 2014 - Top US officials Wednesday upped pressure on key Iraqi leaders as political chaos in Baghdad clouded American hopes for a unity government to tackle the country's sectarian breakdown.

President Barack Obama, meanwhile widened the US effort to convince key regional powers to prevail on Iraqi factions for a political settlement, calling Saudi Arabia's King Abdullah.

Vice President Joe Biden, who frequently burns up the phone lines to Baghdad, talked to the speaker of Iraq's previous parliament, Osama al-Nujaifi, a prominent Sunni leader.

Secretary of State John Kerry meanwhile met a Kurdish delegation in Washington and also spoke to Iraqi Kurdish leader Massud Barzani by phone.

The White House said Biden and Nujaifi agreed on the importance of Iraqis "moving expeditiously to form a new government capable of uniting the country."

Kerry stressed the important role that the Kurds would play in a new multi-sect government in Baghdad, which Washington says is vital to meeting the challenge of Sunni Islamic State (IS) jihadists who have seized vast tracts of Iraqi territory in recent months.

Barzani last week warned that there was no going back on Kurdish rule in the oil-rich northern city of Kirkuk and other towns now defended by Kurdish fighters against Sunni militants.

He also pledged, in an interview with the BBC, to hold an independence referendum within months, raising the specter of the break-up of Iraq.

State Department spokeswoman Jen Psaki said Kerry emphasized with Barzani the urgency of Kurdish "participation in the government formation process (and) the important role the Kurds (are) playing moving forward."

The first session of Iraq's new parliament, dedicated to choosing a new government, broke up in chaos on Tuesday, with lawmakers walking out and making threats, despite the gravity of the political and security situation.

Many Sunni and Kurdish deputies walked out, causing a quorum to be lost, so a speaker could not be elected, and the session ended in disarray.

Washington has made no secret of the fact that it does not believe Shiite Prime Minister Nuri al-Maliki is the man to lead the new government, blaming him for pursuing sectarian policies in the past -- which the US government believes helped prepare the ground for the IS advance.

But no consensus has emerged on who should succeed Maliki and the prime minister seems determined to cling to power.

Under a de facto agreement, in Iraq, the premier of the government is a Shiite Arab, the speaker Sunni Arab and the president a Kurd.

Obama and Abdullah agreed on the need for separate Iraqi factions to unite to form a politically viable government, the White House said.

"The President thanked the King for Saudi Arabia's pledge of $500 million dollars to help alleviate the suffering of all Iraqis who have been displaced by the violence," said a White House statement.