BAGHDAD The dust had barely settled from the last column of departing U.S. armoured vehicles when Iraq's rival Sunni and Shi'ite factions resumed the kind of political infighting that threatens a lurch back into turmoil.
Within hours of the last U.S. troops rolling out of Iraq on Sunday, Shi'ite Prime Minister Nuri al-Maliki had asked parliament to sack his Sunni deputy, and security sources said an arrest warrant was issued for the Sunni vice president.
Add to this a parliamentary boycott announced Saturday by the secular Iraqiya bloc, backed by many Sunnis, and the risk is growing of an intensified power struggle between Sunni, Shi'ite and Kurdish politicians that could leave Iraq vulnerable to meddling by Sunni Arab nations and Shi'ite Iran.
"This political dispute between the different blocs especially Iraqiya and (Maliki), needs to be resolved... to fill the security vacuum left in the country by the Americans," said political analyst Kadhim al-Meqdadi.
"Otherwise if it turns into a power struggle, it would open the door for foreign interference. Every party will go to a country... this is very dangerous for Iraq."
Iran and Turkey, a Sunni Muslim country with a secular constitution, are both major investors and influential players in Iraqi politics. They will be watching with Sunni-led Gulf nations to see how Iraq handles its sectarian and ethnic tensions, especially as the crisis in neighboring Syria threatens to spill over its borders.
Shi'ite politicians fret unrest in Syria could oust Assad and bring to power hardline Sunnis eager to put their weight behind fellow-Sunnis in Iraq.
Uneasy power-sharing with Sunni and Kurdish blocs is not the only test for Maliki as security concerns, territorial disputes and possible popular unrest loom on the horizon now U.S. troops have left Iraq nearly nine years after the 2003 invasion that toppled dictator Saddam Hussein.
The country is struggling with stubborn insurgency and festering discontent over the pace of development. Plagued by daily bombings, decades-old laws, bureaucracy, and crumbling infrastructure, it must attract billions of dollars of foreign investment to rebuild its battered economy.
Maliki must tread carefully over the next months and prove Iraq is able to stand alone and define its place in the Arab region despite discontent in his coalition government and public anger over lack of jobs and poor basic services.
"Iraq faces an endless list of challenges... There is little to suggest that Iraq's government will manage, or be willing, to get itself out of the current stalemate," said Gala Riani, an analyst at IHS Global Insight.
Sunni-backed Iraqiya said it was suspending its participation in parliament over what it called Maliki's failure to deliver on promises. Maliki's office then called on parliament for a vote of no confidence in his Sunni deputy, Vice President Saleh al-Mutlaq, a prominent leader of Iraqiya, saying he lacked faith in the political process.
Iraq's Sunni minority are chafing under what they see as the increasingly authoritarian control of Maliki's coalition. Some local leaders are already pushing mainly Sunni provinces such as Salahuddin and Diyala to demand autonomy from Baghdad.
A dispute between the semi-autonomous Kurdish region and Maliki's central government over oil and territory is also brewing, and is a potential flashpoint after the buffer of the American military presence is gone.
The Kurdistan Regional Government last month stepped up pressure on Maliki's central government by signing exploration deals with Exxon Mobil, a move Baghdad said was illegal. That move is testing Maliki's resolve to centralise control over oil resources.
"Iraq faces a host of challenges... Maliki is moving increasingly to solidify his Shi'ite power base," said Wayne White, a scholar at the Middle East Institute in Washington. "This raises the potential for greater ethno-sectarian friction."
Another challenge ahead is rising public anger about poor services, such as food rationing and a lack of electricity and jobs. The longer it takes to address these complaints, the more the perception may grow that democracy in Iraq does not work, raising the risk of public disturbances.
"The likeliest outcome in Iraq is that the government of Iraq will muddle along imperfectly and inelegantly, with continued but non-catastrophic violence and slow but non-zero economic and political development, in spite of the U.S. withdrawal," said Stephen Biddle, of the Council on Foreign Affairs, a Washington-based think-tank.
"The problem is that the likeliest case isn't the only possibility. And many other possible outcomes are much worse - including renewed civil warfare, a descent back to 2006-scale violence, regional intervention, and a wider war."
(Writing by Rania El Gamal; additional reporting by Patrick Markey; editing by Mark Trevelyan)