Central Command Commander General Kenneth McKenzie told a conference that the continuing US presence has successfully limited the activities of Iran and the Islamic State.

Iran has recently curtailed attacks, McKenzie said, "based on the hope that we would be asked to leave Iraq through the government of Iraq's political processes."

However, he said, "the government of Iraq has clearly indicated it wants to maintain its partnership with the United States and coalition forces as we continue to finish the fight against ISIS."

Speaking to an online conference held by the National Council on US-Arab Relations, McKenzie cited estimates that the Islamic State still has a body of 10,000 supporters in the Iraq-Syria region and remains a real threat.

"The progress of the Iraqi Security Forces has allowed has allowed the United States to reduce force posture in Iraq," he said.

But US and coalition forces have to be there to help prevent Islamic State from reconstituting as a cohesive group able to plot major attacks, he said.

"When you're running for your life up and down the Euphrates River Valley, listening to the noise of an armed MQ-9 drone overhead, it's hard to think about conducting attack planning against Detroit."

McKenzie said the US presence and measured retaliations had also successfully deterred Iran from persisting in attacks on Gulf shipping, and limited its proxy attacks in Iraq.

"Today I believe Iran has been largely deterred because the regime now understands we possess both the capability and the will to respond," he said.