WASHINGTON — When the Bush administration invaded Iraq seven years ago, it pledged to leave behind a democracy that would be a model for the Middle East.

Instead, it now appears that the United States will leave behind a big question mark.

Sunday's parliamentary elections in Iraq will start the clock on the withdrawal of U.S. troops, with 50,000 soldiers remaining in an advisory role after Aug. 31 and all of them gone by the end of 2011, if current plans hold.

The elections are, in a sense, the final act of a U.S.-led invasion that the George W. Bush White House sold on false pretenses — nonexistent weapons of mass destruction, an imaginary nuclear-weapons program and fictional al-Qaida ties — and that has cost nearly 4,400 American lives, at least 100,000 Iraqi ones, as much as $3 trillion and untold political capital.

Senior U.S. officials and top generals, using football terminology, like to speak of the American effort in Iraq as being in the "red zone," close to the goal line of a reasonably stable and democratic country after years of struggle and sacrifice.

However, others who have spent significant time in Iraq say that the country's future, while vastly more hopeful than it was four years ago, is nonetheless still in doubt.

"This can go either way. And it can go either way for a long time to come," said Ryan Crocker, the U.S. ambassador in Baghdad from 2007 to 2009.

Crocker liked to say that the important events of the Iraq war might not have even happened yet.

"I believed it then. I believe it now," he said.

Violence in Iraq is down markedly, but political, ethnic and secular reconciliation has remained elusive. The fault line between Sunni Muslim Arabs and Sunni Kurds still tears at the country's northern tier. Iraq's neighbors, particularly Shiite Muslim Iran and Sunni-dominated Saudi Arabia, see it as a potential regional battleground.

The elections, in which 6,200 candidates are vying for 325 parliament seats, will open a months-long effort to form a new government. That path will be strewn with pitfalls and could stretch beyond the self-imposed Aug. 31 U.S. deadline for withdrawing combat brigades.

The situation is so fragile that President Barack Obama is hearing more calls to consider slowing the troop withdrawal if Iraq takes a turn for the worse.

During a recent visit to Washington, Army Gen. Raymond Odierno, the commander of American forces in Iraq, signaled that he might ask Obama to keep one combat brigade, about 3,000 troops, in the powder-keg city of Kirkuk, on the Arab-Kurdish fault line, after Sept. 1. If he does, he's expected to ask for them this summer, defense officials told McClatchy Newspapers.

However, Obama, who pledged during his election campaign to withdraw U.S. forces from Iraq, appears determined to keep to the schedule no matter what.

"We see nothing now that affects the plan. We're on track to move down to 50,000 troops at the end of August and to end the combat mission. And we don't see anything that will get us off that track," a senior administration official, who briefed reporters on White House-imposed conditions of anonymity, said Thursday.

Sometime this spring, there will be more U.S. troops in Afghanistan than there are in Iraq for the first time since March 2003. There are now 96,000 in Iraq and 78,000 in Afghanistan.

Wayne White, the State Department's principal Iraq analyst from 2003 to 2005, said American influence in Iraq had plummeted — he termed it "nil to iffy" — and that there was little point in extending the U.S. stay.

"If Humpty Dumpty is going to fall apart ... there's very little that the United States is going to be able to do about it," White said.

What the United States will leave behind "is not predictable. But that shouldn't stop us from expediting our withdrawal," he said.

This is the first election since 2003 that the Iraqis have organized themselves. The mere fact that Iraq is holding it, with no major sects or ethnic groups boycotting, is little short of a miracle to many current and former officials who lived through the sectarian violence from 2005 to 2007.

Political killings have dropped dramatically since the Bush administration belatedly changed course in Iraq in early 2007, adopting a counterinsurgency strategy and sending an additional 20,000 combat troops to Iraq.

It remains to be seen whether those gains will outlast the U.S. military's stay.

The course change "basically salvaged a war that we were on the threshold of losing," said Michael O'Hanlon, a scholar at the Washington-based Brookings Institution who initially was skeptical of the troop "surge" but became a leading public proponent.

O'Hanlon said he was now optimistic, but added, "I'm not one of these people who's just jumping from the rooftops these days with joy, because there's still much that can go awry."

For that reason, he said, the White House "should stay flexible" and consider keeping troops in Iraq past December 2011. That would mean amending a U.S.-Iraqi status-of-forces agreement.

Even as American combat forces leave, the United States will have to expend more treasure, time and maybe even blood to secure the gains of the last three years.

The remaining 50,000 troops will be in Iraq in an advisory capacity.