Ammar Al Shamary and John Dyer

Special for USA TODAY

BAGHDAD – An al-Qaeda splinter militia's advances on the capital threatened to trigger a new Sunni-vs.-Shiite civil war Thursday. As independent Kurdish forces aligned with Iraq's military joined the fight, the United States mulled requests to aid the collapsing Iraqi army.

"We have to deal with what is clearly an emergency situation in Iraq," President Obama said Thursday. "I don't rule out anything, because we do have a stake in making sure that these jihadists are not getting a permanent foothold in either Iraq or Syria."

The White House said the U.S. is not considering ground troops but is weighing airstrikes. The U.S. is flying drones over Iraq for surveillance of the militants, a Pentagon official told USA TODAY, asking not to be named because of the sensitivity of the issue.

The U.S. also evacuated an air base in northern Iraq where it had been training Iraqi security forces.

In downtown Baghdad, thousands of young men gathered near an Iraqi army recruitment center, eager to volunteer to help fend off Islamic State of Iraq and the Levant (ISIL) fighters who have have been seizing key cities in recent days from their strongholds in northern Iraq.

"I came today to present my soul as a gift for this country," said Saef Ahmad, 22. "I want to sacrifice my life for sake of my family. I don't want to stay at home until they reach and kill us."

Since Tuesday, ISIL militants have overrun Mosul, Iraq's second-largest city, and Tikrit, birthplace of Saddam Hussein, plunging the country into turmoil less than three years after the departure of American troops. About 500,000 refugees have fled the fighting, setting the stage for a humanitarian crisis.

"Everything has changed," said Kamal Mustafa in Baghdad. "People are confused. Everybody feels like they are alone and no one will protect them. We are afraid of the next development, but hopefully nothing will happen in Baghdad."

Abu Mohammed al-Adnani, an ISIL spokesman, declared in a recording posted Thursday on the group's website, "We have scores to settle. Do not give an inch of liberated land back. Continue your march. The battle is not yet raging, but it will in Baghdad."

ISIL's victories are calling into question whether Iraqi Prime Minister Nouri al-Maliki's Shiite-dominated government can repel the group's Sunni fighters if they reach the capital, a Shiite stronghold. Iraqi troops have offered little or no resistance to the insurgents.

An estimated 30,000 deserted since Monday, the Iraqi government estimated.

"Iraq is inching toward a civil war because the Iraqi government is not capable of stopping ISIL," said Haleh Esfandiari, a Middle East expert at the Woodrow Wilson International Center for Scholars in Washington. "That might turn into a fight eventually between the Shiites and the Sunni Muslims — something that everybody was trying to avoid."

Aiming to create a Sunni Islamic state spanning Syria and Iraq, ISIL's battle-hardened fighters have been operating with impunity for months in Fallujah and parts of Ramadi along with most of Anbar province in the western half of the country.

They've also been fighting against Syrian President Bashar Assad in that country's civil war. The group originally was affiliated with al-Qaeda until the two organizations split in February over internal disagreements.

As night fell in Iraq, ISIL fighters were laying siege to Samarra, a city about 80 miles north of Baghdad that is home to the Al-Askari Mosque. It is a Shiite Muslim holy site that al-Qaeda forces attempted to destroy in 2006, setting off years of sectarian violence that nearly tore the country apart.

"The morale of my soldiers is very high," said Gen. Sabah al Fatlawi, the Iraqi army commander in Samarra. "We will fight till the last breath. We will not let ISIL desecrate the land of the shrine city of Samara. We will not back off before we defeat the enemy."

Al-Maliki has asked the Iraqi parliament to declare a state of emergency, which would expand his powers to include declaring curfews. But on Thursday, it appeared that too few lawmakers attended the legislative session to reach a quorum. The development further undercut al-Maliki's legitimacy.

Adding to the uncertainty, Kurdish fighters called "peshmerga" announced on Thursday that they were in firm control of Kirkuk, an oil-rich town that has long been at the center of power struggles between Kurds, who operate their semiautonomous region; the central government in Baghdad and other ethnic groups.

The Kurds claim to be working with al-Maliki, but their involvement in the fighting highlighted the central government's weakness.

"Peshmerga forces have helped Iraqi soldiers and military leaders when they abandoned their positions," a Kurdistan Regional Government statement said. "Iraqi security agencies and ministries have been incapable and soldiers and employees were only interested in collecting their salaries."

U.S. officials have expressed alarm over the developments. State Department spokeswoman Jen Psaki said Wednesday that the U.S. likely would give Iraq new assistance to combat insurgents.

Al-Malaki has requested U.S. airstrikes to combat the insurgent advances, Ali al-Mousawi, the government's chief spokesman, said Thursday.

President Obama said Thursday that Iraq needs more help from the U.S. and the international community as it battles insurgents who are threatening to attack Baghdad, and he is considering all options. "I don't rule out anything because we do have a stake in making sure that these jihadists are not getting a permanent foot hold in either Iraq or Syria," he said.

While not providing details, Obama said, "There will be some short-term immediate things that need to be done militarily and our national security team is looking into all the options.

"We have to deal with what is clearly an emergency situation in Iraq," he said.

The U.S. already has expedited weapons sales to Iraq this year, including missiles, ammunition and other supplies to bolster al-Maliki's government.

Iraqi officials have called on residents to take up arms and fight the militants while promising military help. "We are working to resolve this situation," al-Maliki said. "We are reorganizing the security forces."

In Tikrit, ISIL fighters already were establishing a new local government, indicating they expected to stay for good.

"The city is quiet," said Mohammed Hassan, 33, a shopkeeper in Tikrit. "We can see ISIL patrolling with the Iraqi forces' cars. They are holding all the checkpoints abandoned by Iraqi forces. The gunmen are sweeping the market and saying hello to people. They try to be nice to get the support of the city, but there's still a lot of fear."

Contributing: Gilgamesh Nabeel; Luigi Serenelli in Berlin; David Jackson and Tom Vanden Brook in Washington