Baghdad (AP) -- At the root of the stand-off is the unresolved power struggle between Iraq's three main groups -- the majority Shiites and minority Sunnis and Kurds -- following the removal of Saddam Hussain in the US-led invasion of 2003.
Elections in March 2010 were inconclusive. Iraq's Nouri Al Maliki was able to form a national unity government but its component parties do not trust and in some cases detest each other.
The continued impasse has raised the possibility of renewed sectarian violence and hampered plans for rebuilding the country ravaged by a decade of fighting.
Six months after the departure of the last US forces, hopes seem to be fading that oil-rich Iraq can quickly transform into a functioning democracy.
"It's a sensitive and tense situation and anything could go wrong," analyst Joost Hiltermann of the International Crisis Group said of the political crisis.
Al Maliki, a Shiite, is under fire for breaking promises to share power with his partners in a unity government that includes the Sunni-dominated Iraqiya bloc, Kurdish parties and loyalists of radical Shiite cleric Muqtada Al Sadr.
Sunnis who believe he is targeting their leaders with politically motivated prosecutions and Kurds who think he is hostile to their northern autonomy have their own reason to dislike the prime minister.