WASHINGTON — As Iraq edges toward chaos, Joe Biden is having a quiet I-told-you-so moment.

In 2006, Biden was a senator from Delaware gearing up for a presidential campaign when he proposed that Iraq be divided into three semi-independent regions for Shiites, Sunnis and Kurds. Follow his plan, he said, and U.S. troops could be out by early 2008. Ignore it, he warned, and Iraq would devolve into sectarian conflict that could destabilize the whole region.

The Bush administration chose to ignore Biden. Now, eight years later, the vice president’s doom-and-gloom prediction seems more than a little prescient.

Old sectarian tensions have erupted with a vengeance as Sunni militants seize entire cities and the United States faults the Shiite prime minister for shunning Iraq’s minorities. While the White House isn’t actively considering Biden’s old plan, Mideast experts are openly questioning whether Iraq is marching toward an inevitable breakup along ethnic lines.

“Isn’t this the divided Iraq that Joe Biden predicted eight years ago?” read an editorial this week in The Dallas Morning News.

If there’s a measure of vindication for Biden, it’s come at the right time.

After staking his claim to leadership on foreign policy, Biden has watched his record come under sometimes bruising criticism, including former Defense Secretary Bob Gates’ insistence that he’s has been wrong on nearly every major foreign policy decision in four decades.

So the trajectory in Iraq, and the public musings about Biden’s being ahead of the curve, haven’t gone unnoticed by his supporters — even if Biden is staying quiet about his 2006 plan to avoid upstaging President Barack Obama.

“He’s been right,” said former Sen. Ted Kaufman, the longtime Biden aide and confidant. “But you’ll be hard pressed to find an ‘I did this’ or ‘I did that.’ He’s not an ‘I told you so’ kind of guy.”

The Bush administration didn’t pursue Biden’s approach. When the Senate voted overwhelmingly in 2007 to back it, Obama, then a senator from Illinois, didn’t vote. Once in office, Obama and Biden sought to secure an agreement with Iraq to keep some U.S. forces there, but didn’t vehemently pursue it once those talks sputtered.

All the while, Biden has retained a key role in the U.S. response to Iraq, handling the portfolio during the troop drawdown and serving as Obama’s primary liaison to Iraqi leaders.