Washington: While US President Barack Obama had overwhelming public backing when he pulled US forces out of Iraq in 2011, support for that decision now has dropped 14 points, a Gallup poll released found.

The June 20-21 poll comes amid turmoil in Iraq, as fighters from the Sunni group Islamic State of Iraq and Greater Syria (ISIS) are reportedly beheading victims in a bid to instill fear.

In response to the threat of attacking the capital city of Baghdad, Obama has sent 275 military troops to help secure the US embassy and 300 military advisors to assist the Iraqi government.

While the majority of Americans still back the 2011 decision to leave Iraq and 57 percent believe the war was a mistake, the move is being heavily scrutinised in light of the current situation, Xinhua reported citing the poll.