TIMELINE: President Bush makes farewell visit to Iraq

(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.

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

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

March 8, 2004 - 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.

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

March 16 - National Assembly holds first meeting.

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

October 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.

December 15 - Parliamentary election. Sunnis vote in strength.

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

February 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.

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

December 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.

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 build-up, or "surge," to 160,000 soldiers.

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

August 14 - At least three suicide bombers driving fuel tankers kill and wound at least 796 people in Yazidi residential compounds in the villages of Kahtaniya and al-Jazeera in northern Iraq near the Syrian border.

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

January 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.

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

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

July 7 - Maliki for the first time raises the prospect of setting a timetable for the withdrawal of U.S. troops as part of negotiations over a new security agreement with Washington.

July 19 - In a political breakthrough, Iraq's main Sunni Arab bloc rejoins the government after parliament approved its candidates for several vacant ministerial posts.

September 1 - The U.S. military hands over Anbar province to Iraqi security forces, after it almost lost the western region to a Sunni Arab insurgency. Anbar is the first Sunni Arab one to be returned to Iraqi control since 2003. Babil province is returned to Iraqi forces on October 23.

Sept 24. - Parliament approves a provincial elections law. The presidency approves it formally on October 7 paving the way for the vote to take place by January 31, 2009.

Oct 15 - U.S. forces announce they killed the second-in-command of al Qaeda in Iraq, a Moroccan named Abu Qaswarah, in a raid in Mosul on October 5.

Nov 17 - Iraq and the United States sign an accord requiring Washington to withdraw its forces by the end of 2011. The pact gives the government authority over the U.S. mission for the first time, replacing a U.N. Security Council mandate.

Nov 27 - Parliament approves pact after protracted negotiations between rival factions, removing the last major hurdle to the deal.

Dec 2 - An Iraqi court sentences "Chemical Ali" to death for the killing of thousands of Shi'ites in a ruthless crackdown on their uprising after the 1991 Gulf War.

Dec 11 - A suicide bomber detonates explosives inside a Kurdish restaurant north of Kirkuk. At least 50 people are killed and 109 wounded in the blast.

Dec 14 - U.S. President George W. Bush makes an unannounced farewell visit to Baghdad weeks before he leaves office to bequeath the unpopular Iraq war to President-elect Barack Obama.