"[M]any Senators came to wish they had voted against the resolution. I was one of them. As the war dragged on, with every letter I sent to a family in New York who had lost a son or daughter, a father or mother, my mistake become (sic) more painful," Clinton wrote.

"I thought I had acted in good faith and made the best decision I could with the information I had. And I wasn't alone in getting it wrong. But I still got it wrong. Plain and simple," she added.

The vote to authorize military action in Iraq dogged Clinton with the Democratic Party's antiwar activist base in the 2008 presidential primaries.

Clinton's rival, Barack Obama, opposed the Iraq war from the start. He gave a speech in 2002 when he was still an Illinois state senator, opposing the war.

Clinton failed to distance herself from the vote, but she stopped short of saying she regretted casting it.

In 2003, the United States invaded Iraq in blatant violation of international law and under the pretext of finding weapons of mass destruction allegedly stockpiled by former Iraqi dictator Saddam Hussein.

A War Crimes Tribunal in Malaysia in 2011 found former US President George W. Bush and former British Prime Minister Tony Blair guilty of war crimes for their roles in the Iraq war.

The tribunal judges also stated that the US, under the leadership of Bush, fabricated documents to make it appear that Iraq possessed weapons of mass destruction.

However, the world later learned that the former Iraqi regime did not possess WMDs and that the US and British leaders knew this all along.

Over one million Iraqis were killed during the invasion, according to the California-based investigative organization Project Censored.

RA/MB