CHRONOLOGY-Iraq from invasion to brink of civil war

April 9 (Reuters) - Following is a chronology of key events in Iraq since the U.S.-led invasion in 2003 that toppled Saddam Hussein.

March 20, 2003 - U.S. and British forces invade from Kuwait.

April 9 - U.S. troops take Baghdad, Saddam disappears.

July 13 - The Iraqi Governing Council -- 25 Iraqis chosen under U.S. supervision -- holds inaugural meeting in Baghdad.

Aug. 19 - Suicide truck bomb wrecks U.N. headquarters in Baghdad, killing 22 people, including U.N. envoy Sergio Vieira de Mello.

Aug. 29 - A car bomb kills at least 83 people, including top Shi'ite Muslim leader Ayatollah Mohammed Baqer al-Hakim, at the Imam Ali mosque in Najaf.

Dec. 13 - U.S. troops capture Saddam near Tikrit. U.S. governor Paul Bremer breaks news with: "We got him."

March 2, 2004 - 171 people are killed in twin attacks in Baghdad and Kerbala.

March 8 - Iraq Governing Council signs interim constitution.

June 1 - Governing Council dissolved to make way for interim government led by Iyad Allawi. Ghazi al-Yawar named president.

June 28 - United States formally returns sovereignty. Coalition Provisional Authority dissolved. Bremer leaves Iraq.

Jan. 30, 2005 - Shi'ite-led United Alliance dominates election for interim parliament. Most Sunnis don't vote.

March 16 - National Assembly holds first meeting.

Oct. 15 - Referendum ratifies constitution by 78 percent despite Sunni Arab opposition which nearly vetoes it.

Oct. 19 - Saddam goes on trial charged with crimes against humanity for the killing of 148 Shi'ite men and boys in Dujail after a 1982 assassination attempt. He pleads not guilty.

Dec. 15 - Parliamentary election. Sunnis vote in strength.

Feb. 10, 2006 - Final results give Shi'ite Alliance near majority with 128 seats. Sunnis have 58 and Kurds 53.

Feb. 22 - Destruction of Shi'ite shrine in Samarra sparks widespread sectarian violence, raising fears of civil war.

May 21 - New Prime Minister Nuri al-Maliki chairs first cabinet meeting.

June 7 - U.S. aircraft kill al Qaeda leader in Iraq, Abu Musab al-Zarqawi.

Nov. 5 - A court in Baghdad finds Saddam guilty of crimes against humanity and sentences him to hang over Dujail killings.

Nov. 23 - Six car bombs in different parts of the Sadr City neighbourhood of Baghdad kill 202 people.

Dec. 30 - Saddam is executed.

Feb 14, 2007 - Maliki launches U.S.-backed crackdown in Baghdad aimed at pulling Iraq back from brink of civil war.

April 18 - Multiple car bombings kill 191 people around Baghdad. At the Sadriya market, one bomb alone kills 140 people.

May 28 - Iranian and U.S. ambassadors to Iraq meet in Baghdad to discuss ways to improve security in the country. The talks end a three-decade diplomatic freeze between the two foes.

June 15 - U.S. military says it has completed its troop buildup, or "surge", to 160,000 soldiers.

Aug. 1 - The main Sunni Arab bloc pulls out of Maliki's cabinet, plunging the government into crisis.

Aug. 14 - Truck bombings against the minority Yazidi community in northern Iraq kill 411 people. The bombings are the deadliest militant attacks in Iraq since the U.S.-led invasion.

Aug. 29 - Shi'ite cleric Moqtada al-Sadr imposes ceasefire on Mehdi Army militia for six months after clashes with police.

Sept. 3 - U.S. President George W. Bush makes a surprise visit to Iraq, and raises the prospect of troop cuts in the wake of falls in violence.

Sept. 10 - The U.S. military commander in Iraq, General David Petraeus, recommends cutting American troops by more than 20,000 by mid-2008 in much anticipated testimony to Congress.

Sept. 13 - Sheikh Abdul Sattar Abu Risha, a Sunni Arab tribal leader instrumental in driving al Qaeda out of Anbar province, is killed in a bomb attack.

Jan. 12, 2008 - Parliament votes to let members of Saddam's Baath Party return to government jobs, winning U.S. praise for achieving a benchmark step toward reconciling warring sects.

Feb. 21 - Thousands of Turkish troops cross into northern Iraq in their hunt for Kurdish PKK guerrillas. Eight days later Turkish forces withdraw.

Feb. 22 - Sadr extends Mehdi Army truce by another 6 months.

March 25 - Maliki launches crackdown on militias in Basra, sparking pitched battles with Sadr's Mehdi Army. Fighting rages for a week in southern Iraq and Baghdad. Hundreds are killed.

April 8 - Sadr threatens to scrap Mehdi Army truce.

- Petraeus tells Congress he plans to halt U.S. troop withdrawals in July because of fragile security gains. (Writing by David Cutler, Editing by Dean Yates, London Editorial Reference Unit)