90 walk out in Iraq parliament

• The parliament can't continue because too many members failed to return


• Many expected the Prime Minister to call for the formation of a new government


• U.N.: More than 2,400 Iraqis, including 1,500 civilians, were killed last month


• The United States is sending 300 more troops to Baghdad for protection

Baghdad, Iraq (CNN) -- After much anticipation over how it would address the country's turmoil, Iraq's new parliament postponed its first session until next week, citing a lack of a quorum.

The move came after 90 members of parliament failed to return after a 30-minute morning break during the scheduled session Tuesday.

"We are going to postpone because of an urgent matter," the speaker of the parliament said. He did not say what the urgent matter was, and it was not immediately clear what happened.

The newly elected parliament convened with 255 out of 328 elected officials attending, which was enough for a legal quorum, the speaker said. But when many failed to return after the break, there were not enough members to continue.

Many expected Prime Minister Nuri al-Maliki to call for the formation of a new government Tuesday as Iraq battles militants from the Islamic State in Iraq and Syria.

Mass graves and executions shock Iraq

An Iraqi child walks through a displacement camp for those caught-up in the fighting near the city of Mosul on Saturday, June 28 in Khazair, Iraq. Vast swaths of northern Iraq, including the cities of Mosul and Tal Afar, have fallen as the Islamic State in Iraq and Syria, or ISIS, advances toward Baghdad, the capital. The ISIS militants want to establish a caliphate, or Islamic state, in the region, stretching from Iraq into northern Syria.

An Iraqi woman walks with her child outside of a displacement camp on June 28 in Khazair, now home to an estimated 1,500 internally displaced persons.

Peshmerga fighters, or Kurdish warriors, check cars at the entrance to a temporary displacement camp in Khazair, Iraq, for people caught in the fighting in and around the city of Mosul on Thursday, June 26.

A group of women wait outside the temporary displacement camp in Khazair on June 26.

Smoke rises in the Karakus district of Mosul as clashes between Iraqi forces and ISIS militants on June 26.

Food is handed out at the displacement camp in Khazair.

A child walks over discarded water bottles and trash at a registration area at the displacement camp in Khazair on June 26.

Kurdish Peshmerga take their positions behind a wall on the front line of the conflict with ISIS militants in Tuz Khormato, Iraq, on Wednesday, June 25.

Peshmerga fighters clean their weapons at a base in Tuz Khormato, Iraq, on June 25.

Female Peshmerga between 18 and 45 years old form a special unit that is called to serve in any conditions. A soldier is pictured here on June 25.

A woman gathers bread in a temporary displacement camp for Iraqis caught up in the fighting in and around Mosul on Tuesday, June 24.

An ISIS fighter takes control of a traffic intersection in Mosul on Sunday, June 22.

An ISIS member distributes a copy of the Quran, Islam's holy book, to a driver in Mosul on June 22.

Members of ISIS patrol in Falluja, 40 miles west of Baghdad, on Saturday, June 21.

Volunteers raise their weapons and chant slogans during a parade in the Shiite stronghold of Sadr City, Baghdad, on Saturday, June 21.

Iraqi men register to volunteer to fight alongside security forces against Sunni Muslim militants and jihadists on Friday, June 20, at a recruitment center in Baghdad.

New Iraqi army recruits gather in Najaf on Wednesday, June 18, following a call for Iraqis to take up arms against Islamic militant fighters.

Soldiers with an Iraqi anti-terrorism unit are on guard June 18 in Baghdad.

A Kurdish Peshmerga fighter injured in clashes with members of ISIS lies in a hospital in Irbil on June 18.

An MH-60R Sea Hawk helicopter lands on the aircraft carrier USS George H.W. Bush in the Persian Gulf on Tuesday, June 17. The carrier moved into the region to give President Barack Obama "additional flexibility," the Pentagon has said.

Newly recruited Iraqi volunteer fighters take part in a training session in Karbala on June 17.

Iraqi tribesmen gather in Baghdad on Monday, June 16, to show their readiness to join Iraqi security forces in the fight against Islamic militants.

Iraqi Christian children gather inside the Church of the Virgin Mary for prayers in Bartala, Iraq, a town near Mosul, on Sunday, June 15. Militants seized Mosul last week, reportedly leading more than 500,000 people to flee Iraq's second-largest city.

Shiite tribal fighters raise their weapons and chant slogans against ISIS in Basra, Iraq, on June 15.

Members of ISIS prepare to execute some soldiers from Iraq's security forces in this image, one of many reportedly posted by the militant group online. CNN cannot independently confirm the authenticity of the images.

A woman cradles her baby Thursday, June 12, at a temporary camp set up in Aski Kalak, Iraq, to shelter those fleeing the violence in northern Nineveh province.

A girl fleeing from Mosul arrives at a Kurdish checkpoint on June 12.

Iraqi men chant slogans outside of an army recruiting center to volunteer for military service June 12 in Baghdad.

Kurdish Peshmerga forces, along with Iraqi special forces, deploy their troops and armored vehicles outside of Kirkuk, Iraq, on June 12.

Children stand next to a burnt vehicle during clashes between Iraqi security forces and ISIS militants in Mosul on Tuesday, June 10.

Civilians from Mosul escape to a refugee camp near Irbil, Iraq, on June 10.

Iraqis fleeing the violence wait in their vehicles at a Kurdish checkpoint in Aski Kalak on June 10.

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Photos: Iraq under siege

Feinstein: Iraqi state is in danger

Al-Maliki and his Shiite-dominated government have been under pressure by Western and Arab diplomats to be more inclusive of Iraq's Sunni minority, who say they have been marginalized and cut out of the political process by the government.

Under Iraq's constitution, the parliament has 75 days from when it convenes to pick a prime minister.

Lawmakers are under pressure to move faster, but the political body has had trouble moving swiftly in the past. The last time parliament met to pick a prime minister, it took nearly 10 months.

American and Arab diplomats have told CNN that the United States probably won't launch military strikes against ISIS and its allied fighters before a new government is formed in Iraq.

Russia sends 5 fighter jets to Iraq, al-Maliki criticizes U.S.

U.S. sends more troops to Iraq

But the United States is increasing its military presence in Iraq, ordering 300 more troops to the besieged country, the Pentagon announced Monday.

ISIS militants have "continued to pose a legitimate threat to Baghdad and its environs," a U.S. official told CNN. "We have seen them reinforce themselves around Baghdad enough to convince us more troops was the prudent thing to do."

The new troops, 200 of whom arrived Sunday and Monday, will provide security for the U.S. Embassy, the Baghdad airport and other facilities in Iraq, Pentagon spokesman Rear Adm. John Kirby said.

The deployment includes "a detachment of helicopters and unmanned aerial vehicles, which will bolster airfield and travel route security," Kirby said in a written statement.

The airport is in western Baghdad about 12 miles (20 kilometers) by helicopter from the embassy in the capital's fortified International Zone, commonly known as the Green Zone.

The 300 troops are in addition to 300 U.S. advisers who will help train Iraq's security forces. They will bring the total of American forces in Iraq to about 800 troops.

Staggering death tolls

Expert: This looks like mission creep

Iraq executions, atrocities on both sides

The magnitude of the Iraq crisis can be illustrated in the sharp rise in deaths over the past two months.

At least 2,417 Iraqis died in violence in June, according to the United Nations Assistance Mission for Iraq.

Of that total, of 1,531 were civilian deaths (including 270 civilian police) and 886 were members of the Iraqi security forces, UNAMI said.

The June death toll is more than double the number of deaths from May, which was 994, according to the United Nations. At least 144 of those killed in May were civilian police officers.

Iraq claims victories against militants

While ISIS has seized swaths of Iraq in recent weeks, Iraqi forces have made strides in battling the militants, the government said.

The military has said it has been battling to retake Tikrit, the birthplace of former Iraqi dictator Saddam Hussein and the capital of Salaheddin province, from ISIS. The military cleared the University of Tikrit of militant fighters, state-run media said Tuesday.

The Iraqi government also said Tuesday that the military killed 32 militants on the outskirts of Tikrit as part of a major offensive in Salaheddin.

Iraqi state TV also said a pro-government tribal council has been established in the oil-rich city of Kirkuk, an area that has been hotly contested.

CNN cannot independently confirm the government claims.

ISIS declares caliphate

Emboldened by a weakened Iraqi government that is struggling to stop their murderous advance, extremists from the Islamic State in Iraq and Syria declared over the weekend that they have set up a caliphate -- or Islamic state -- spanning large areas of the two countries.

In a newly released audio message and written statement purportedly from the ISIS spokesman, the group called on Muslims to swear allegiance to the caliphate. Both Shia and Sunni Muslims have been deeply offended by the claim.

The message claims that the group's territory now spans from Aleppo province in northwestern Syria to Diyala province in eastern Iraq. It announced that ISIS was changing its name to just the "Islamic State."

Allegations of atrocities

Human Rights Watch, citing displaced residents and local activists and journalists, said Saturday that ISIS fighters kidnapped at least 40 Shiite Turkmen, dynamited four Shiite places of worship and ransacked homes and farms in two villages just outside Mosul.

Earlier in the week, in the predominantly Shiite Turkmen city of Tal Afar, about 50 kilometers (31 miles) west of Mosul, ISIS destroyed seven Shiite places of worship, Human Rights Watch said, citing local sources.

But allegations of atrocities are not just limited to ISIS. Amnesty International has said it has gathered evidence pointing to a pattern of "extrajudicial executions" of Sunni detainees by government forces and Shiite militias in Tal Afar, Mosul and Baquba.

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CNN's Chelsea J. Carter reported from Baghdad; Holly Yan reported and wrote from Atlanta. CNN's Ali Younes, Steve Almasy, Barbara Starr and Mohammed Tawfeeq contributed to this report.