Military officers from more than 30 countries in the US-led coalition against the Islamic State group will meet Wednesday at a US base to plan the war effort against the jihadists, the American military said.

Nearly 200 military planners will gather for more than a week at MacDill Air Force Base in Tampa, Florida, home to US Central Command, which is overseeing the air war against the IS group in Iraq and Syria.

"The conference provides an opportunity for coalition partners to strengthen relationships and further develop and refine military campaign plans to degrade and defeat ISIL," Central Command said in a statement, using an alternative acronym for the extremist group.

Commanders from more than 20 coalition partners met about a month ago in Washington and the session starting this week represented another "milestone," Central Command said.

"The nearly 200 participants represent the broad coalition that has come together and is key to the success of our campaign to defeat ISIL," General Lloyd Austin, head of Central Command, said in the statement.

"Indeed, it is the coalition that our enemies fear most. And, it is the coalition that will get the job done and done the right way, and as quickly as possible."

The meeting, which will run through November 21, comes more than three months since US warplanes launched bombing raids against the IS group in Iraq and after more than 800 air strikes in Iraq and Syria, most of which have been conducted by American aircraft.

The military planning session also follows President Barack Obama's decision to send an additional 1,500 US troops to Iraq to advise and train government forces and Kurdish militia, amid plans to help the Iraqi army eventually seize back territory from the IS militants.

Despite the daily air raids, the IS group has continued to advance in some areas and has yet to be driven back from key towns it seized over the past several months in Iraq and Syria.

The IS fighters have declared an Islamic "caliphate" over large swathes of territory under their control, and pursued a campaign of mass executions and atrocities to sow fear and discourage resistance.