BAGHDAD - Iraq's prime minister called a crisis conference in a bid to open a dialogue Tuesday among Iraq's divided factions, shore up his shaky government and unstick the stalled political process.

The U.S. military, meanwhile, pressed its crackdown on violence, announcing a new offensive against extremists on both sides of the sectarian divide -- an operation called Phantom Strike to build on the successes during recent offensives in Baghdad and surrounding areas.

The American statement singled out Sunni insurgents linked to al-Qaida in Iraq and said the Shiite extremists were being backed by Iran. The military has stepped up its rhetoric recently against Iran, which is accused of supplying militias with arms and training to attack U.S. forces. Iran denies the allegations.

The military statement did not give details but said U.S. forces would increase pressure on al-Qaida and its Sunni militant allies and rogue Shiite militiamen nationwide. Many of those fighters have fled the six-month-old crackdown in Baghdad and central Iraq and were believed to be trying to operate farther afield.

"My intent is to continue to pressure AQI and other extremist elements throughout Iraq to reduce their capabilities," said the U.S. second-in-command, Lt. Gen. Ray Odierno.

Prime Minister Nouri Al-Maliki called for the crisis meeting during a news conference Sunday and said he hoped it could take place in the next two days as he faces growing impatience with his government's perceived Shiite bias and failure to achieve reconciliation or to stop the sectarian violence threatening to tear the country apart.

It was a limited invite, including President Jalal Talabani, a Kurd, Vice President Tariq al-Hashemi, a moderate Sunni, Vice President Adel Abdul-Mahdi, a Shiite, and Massoud Barzani, the leader of the autonomous Kurdish region in northern Iraq.

But each leader wields strong influence over their respective sect or ethnic group and the move appeared to be a bid by al-Maliki to sideline his staunchest opponents by bringing moderates into the fold.

A government official, speaking on condition of anonymity because he wasn't authorized to release the information, said the five officials would meet Tuesday to try to come up with a blueprint on how to pull the government out of its crisis and reach agreement on divisive issues such as sharing Iraq's oil riches and de-Baathification.

The prime minister also threatened to isolate the political blocs who have boycotted his Cabinet, suggesting they could be replaced by local Sunni tribal leaders who have recently formed alliances and joined U.S.-led efforts against al-Qaida in Iraq.

"We hope to end this crisis and that the ministers will return," al-Maliki said. "But if that doesn't happen, we will go to our brothers who are offering their help and we will choose ministers from among them."

A senior U.S. official in Iraq, who also declined to be identified because of the sensitivity of the issue, said the meeting would pave the way for Iraq's leadership to make fundamental changes needed to jump-start political reconciliation.

"This isn't a one-off kind of thing," the official said. "A lot of this is developing mechanisms which can be used, not instant solutions but understandings that the solutions are going to be needed over time. And making a commitment to a mechanism, a process and keeping at that process until Iraq is in a better place."

He said U.S. Ambassador Ryan Crocker would be available for consultations if needed but would not participate in the meetings, which he called an Iraqi initiative.

Iraq's minority Sunnis expressed growing anger over their perceptions of al-Maliki as a deeply biased sectarian leader with links to Iran and his failure to bring all sides together after taking office in May 2006 and promising a national unity government.

"It is one year and 4 months now that he has been in office and he is still leading a one-man rule and a sectarian policy," said Hamid al-Mutlaq, a senior member of the National Dialogue Front, a Sunni Arab political party. "The country is on the verge of collapse."

"Is he going to give a cure after all this destruction? He has proved that he is a sectarian leader and a failure, the country is under the control of criminal gangs with the complete absence of an authority or government."

His sharp words came a day after Iraq's most senior Sunni politician, Adnan al-Dulaimi, issued a desperate appeal for Arab nations to help stop what he called an "unprecedented genocide campaign" by Shiite militias armed, trained and controlled by Iran.

Al-Dulaimi said "Persians" and "Safawis," Sunni terms for Iranian Shiites, were on the brink of total control in Baghdad and soon would threaten Sunni Arab regimes which predominate in the Mideast.

"It is a war that has started in Baghdad and they will not stop there but will expand it to all Arab lands," al-Dulaimi wrote in an impassioned e-mail Sunday to The Associated Press.

The 75-year-old al-Dulaimi heads the Iraqi Accordance Front, the largest Sunni political bloc in parliament. The coalition of parties pulled its six Cabinet ministers from al-Maliki's Shiite-dominated government Aug. 1.

Five days later, government ministers loyal to former Prime Minister Ayad Allawi, a secular Shiite, launched a boycott of Cabinet meetings. That left the government without any Sunni Arab members, except the politically unaffiliated defense minister.

In violence Monday, Iraqi police and hospital officials said four civilians were killed and 10 wounded in a roadside bombing that targeted U.S. forces and a subsequent shoot-out in a predominantly Shiite area in eastern Baghdad. The U.S. military said it was looking into the report.

Iraqi judicial authorities also said the third trial against former officials with Saddam Hussein's ousted regime would begin on Aug. 21. Saddam's cousin Ali Hassan al-Majid, known as "Chemical Ali," and 14 other defendants will face charges in the brutal crushing of a Shiite uprising after the 1991 Gulf War.