U.S. troops to remain as combat role endsSTORY HIGHLIGHTS- NEW: The U.S. combat mission in Iraq is over
- Obama says the main message in his speech will be to thank the troops
- Obama will address the transition in an Oval Office speech at 8 p.m. ET
- Republicans are criticizing Obama for opposing George W. Bush's military "surge"
Watch President Obama's speech live on CNN at 8 p.m. ET Tuesday, online, on TV and on the CNN App for the iPhone.
Washington (CNN) -- Almost seven and a half years ago, President George W. Bush launched a blistering "shock and awe" invasion of Iraq.
The goal: Eliminate a perceived threat of weapons of mass destruction while replacing a hostile, tyrannical regime with a friendly democracy in the heart of the Middle East.
At 5 p.m. ET -- at a cost of more than 4,400 U.S. military personnel killed and 30,000 wounded -- America's combat mission in Iraq officially drew to a close.
The quick removal of Iraqi leader Saddam Hussein ushered in years of grinding sectarian violence, war, terrorist attacks and, according to some observers, increased Iranian influence in the region. Various groups have estimated the Iraqi civilian death toll to be roughly 100,000 or more. But the war also paved the way for nationwide elections and increasing economic development.
Whether it was worth the price remains a subject of fierce debate both at home and abroad.
Video: Iraq war never over for some 
Video: Biden visits Baghdad 
Gallery: Newsmakers from the Iraq war 
Gallery: Life in Iraq RELATED TOPICS - Iraq War
- U.S. Armed Forces Activities
- George W. Bush
- Barack Obama
President Barack Obama, who based much of his campaign for the White House on growing public exhaustion with the conflict, will announce the conclusion of the combat mission in a speech to be delivered from the Oval Office at 8 p.m. ET. He spent the day meeting with troops at Fort Bliss, Texas -- a base that has supplied soldiers at all stages of the conflict.
Obama called Bush for a "few minutes" from Air Force One while en route to Texas, according to White House Deputy Press Secretary Bill Burton. The White House has not said if Obama will give Bush any credit during his speech for the controversial 2007-08 military "surge," believed by some observers to have helped curtail Iraqi violence.
His remarks are "not going to be a victory lap," Obama told the troops stationed at Fort Bliss. "We still have a lot of work to do."
Obama said his main message will be a simple one to military veterans of the conflict: "Congratulations on a job well done."
Ben Rhodes, a presidential foreign policy speechwriter, told reporters Obama's remarks will focus on -- among other things -- the responsibilities of Iraqi leaders moving forward, as well as the new partnership between the United States and Iraq.
Obama will also discuss the refocusing of U.S. resources in the global fight against al Qaeda, as well as the heightened U.S. military presence in Afghanistan, Rhodes said.
Vice President Joe Biden, who once advocated splitting Iraq along largely ethnic lines, is in Baghdad, Iraq, for the transition. He will also help mark Wednesday's transfer of U.S. military command there from Army Gen. Ray Odierno to Army Lt. Gen. Lloyd Austin.
While the official U.S. combat mission is ending, roughly 50,000 American troops will remain in the country until the end of 2011. Their mission will be to train, assist and advise the Iraqis.
As the U.S. military has been scaling down, the U.S. civilian presence has been ramping up. Iraqi officials are struggling to form a new ruling coalition in the wake of March's closely contested national elections.
While Obama administration officials have touted what they say is a gradual decline in the overall level of violence in Iraq, the country has recently been the target of a series of attacks.
Iraqi Prime Minister Nuri al-Maliki warned Friday of the likelihood of continuing attacks across the country. His warning came two days after 20 bomb attacks struck 13 Iraqi cities, mostly targeting police. The bombs killed 48 and wounded at least 286.
Al-Maliki said there were indications that "al Qaeda and remnants of [Saddam Hussein's] Baath party with foreign backing are planning to carry out a series of bombings in Baghdad and the other provinces."
The attacks -- a show of force for the insurgency -- have increased fears among Iraqis about the ability of their security forces to protect them after the U.S. withdrawal.
But Biden on Tuesday suggested that reports of increased violence in Iraq have been exaggerated by the media.
"Notwithstanding what the national press says about increased violence, the truth is things are still very much different," he told reporters while meeting with al-Maliki. "Things are much safer."
Biden called recent terrorist attempts "dismal."
The Iraqi prime minister marked the occasion on Tuesday with a national address proclaiming his country "sovereign and independent."
Like Biden, al-Maliki said there had been major strides in Iraqi security.
"If these security achievements were not real, we would not have been able to move to executing the bigger and more important step, which is the withdrawal of American forces that is happening today," he said.
"We do not view the withdrawal as an accomplishment of one person, or one party or one sect or one ethnicity; it is an achievement for all Iraqis. ... And it represents a golden opportunity to strengthen national unity and a starting point to build Iraq after decades of destruction and suffering."
Top Republicans were loath to give the Obama White House any credit for Tuesday's milestone.
House Minority Leader John Boehner, R-Ohio, said in a speech delivered Tuesday to the American Legion in Milwaukee, Wisconsin, that the day "belongs to our troops."
In a thinly veiled slap at Obama, Boehner said that "some leaders who opposed, criticized and fought tooth and nail to stop the surge strategy now proudly claim credit for the results."
At a speech in his home state of Kentucky, Senate Republican Leader Mitch McConnell was more direct in his criticism.
"You might recall that the surge wasn't very popular when it was announced. You might also recall that one of its biggest critics was the current president," McConnell said.
"So it makes it easier to talk about fulfilling a campaign promise to wind down our operations in Iraq when the previous administration signs the security agreement with Iraq to end our overall presence there."
Defense Secretary Robert Gates, a holdover from the Bush administration, said during a speech Tuesday to the American Legion that, despite the recent spate of attacks in Iraq, "overall levels of violence this year remain at their lowest point since the beginning of the war in 2003."
"Al Qaeda in Iraq has been largely cut off from its masters abroad."
But Gates stressed that he was not "saying that all is, or necessarily will be, well in Iraq."
"Sectarian tensions remain a fact of life. Al Qaeda in Iraq is beaten, but not gone. This is not a time for premature victory parades or self-congratulation," he said.
CNN's Dana Bash, Ed Henry, Dan Lothian and Suzanne Malveaux contributed to this report