A decade of anger over the Iraq war resurfaced in the 2016 US election race Tuesday, with Jeb Bush and Hillary Clinton's campaigns trading blame about that country's continued instability.

Twelve years after president George W. Bush led the United States into an unpopular and troubled conflict, his brother, now a Republican presidential hopeful, accused Democrats of abandoning Iraq before the job was done.

Jeb Bush accused his Democratic White House rival, former Secretary of State Clinton, of allowing the brutal emergence of the Islamic State group by withdrawing troops from Iraq too fast.

"It was a case of blind haste to get out," Bush told an audience California.

"Rushing away from danger can be every bit as unwise as rushing into danger, and the costs have been grievous."

He noted Clinton only visited Iraq once during her four years as America's top diplomat.

Bush's remarks dredged up a bitter argument that as long bubbled in Washington and that has tarnished his brother's legacy.

A wildly successful invasion of Baghdad was followed by a ham-fisted occupation that fueled brutal sectarian violence and left the central government debilitated.

In addition to being a point of contention between Republicans and Democrats, the war may have also cost Clinton the 2008 Democratic nomination to anti-war candidate Barack Obama.

In 2002 Clinton voted in favor of authorizing Bush's invasion as a Senator for New York, a vote she later said was a mistake.

But on Tuesday her campaign defended her later record.

Long-time foreign policy aide Jake Sullivan — a frontrunner to become her National Security Advisor if Clinton is elected — accused Jeb Bush of a "pretty bold attempt to rewrite history and reassign responsibility."

"They cannot be allowed to escape responsibility for the real mistake here," he said, saying Islamic State emerged form Al-Qaeda in Iraq, which flourished amid the occupation.

"It didn't exist before the invasion. It emerged in no small part as a result of president Bush's failed strategy. And it gained strength by signing up former Sunni military officers – officers from the army that the Bush administration disbanded," he said.

In his speech Bush said that the United States must now take the fight to Islamic State.

"Instead of simply reacting to each new move the terrorists choose to make, we will use every advantage we have to take the offensive, to keep it, and to prevail," he said.

"In all of this, the United States must engage with friends and allies, and lead again in that vital region."

Sullivan challenged Bush to state what actions he would take beyond training rebels and a bombing campaign — which the Obama campaign has launched.

"If that is what he wants — more American boots on the ground in combat in Iraq — he should come out and say so," Sullivan said.