The United States could have prevented the Islamic State from spreading terror in Iraq if the US troops sent there to try and pacify the country had stayed longer before being pulled out.

The contention was aired by Army Chief of Staff Gen. Ray Odierno, the US military leader who is widely regarded as the main architect of the US military operations in Iraq.

The continuing chaos "might have been prevented" if only the US maintained its level of focus in Iraq, Odierno said in an exclusive interview with Fox News.

Odierno, who is only weeks away from his retirement after a 39-year service in the military including a four-year stint in Iraq, said it is "frustrating" to watch the gains he helped achieve in Iraq crumble under ISIS.

The general, who has spent more time in Iraq than any other American army general and served as the top commander in his last two years in Iraq, said the US could have averted the conflict that is now ravaging ISIS-infested countries.

"It's frustrating to watch it," Odierno said. "I go back to the work we did in 2007, 2008, 2009, and 2010 and we got it to a place that was really good. Violence was low, the economy was growing, politics looked like it was heading in the right direction."

"If we had stayed a little more engaged, I think maybe it [rise and spread of ISIS] might have been prevented," he said. "I've always believed the United States played the role of honest broker between all the groups and when we pulled ourselves out, we lost that role."

While still serving as the top commander in 2009, Odierno said he suggested making 30,000-35,000 US troops stay after the end of 2011, when the troops have been scheduled to pull out.

His suggestion, however, fell on deaf ears.

Odierno said: "I think it would have been good for us to stay."

When ISIS captured large Iraqi territories like Mosul, the country's second largest city, he said the White House did not reach out to him despite his experience commanding US forces longer than anyone else.

"All my work was given to [Joint Chiefs] Chairman [Martin] Dempsey," Odierno said. "I never talked directly to the president about it at that time, but I talked to the secretary of defence and I'm sure he relayed all of my thoughts," he added.

In a press release by the US Army last month, Odierno was quoted as saying that fighting ISIS will entail the effort of nations other than the US.

"In order to defeat ISIS, it's going to take an effort of many nations and must be led by the nations in the Middle East. This cannot be a US effort alone," he said.

He added that Iraqi security forces were well-trained until US troops were pulled out of the country in 2011.