(CNN) The upcoming Iraqi assault to retake Mosul from ISIS control could include U.S. military advisers near the front lines.

U.S. military leadership has held open the possibility it would recommend moving advisers closer to combat lines. As the key Mosul battle looms, that remains a potential consideration "if and when they believe it's necessary," a senior U.S. military official tells CNN.

The possible recommendation would need to be approved by President Barack Obama, who has said that U.S. troops will not be sent on a combat mission. But putting advisers with front-line Iraqi troops puts American troops in close range of what is likely to be an intense battle with the terror group.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, and Gen. Lloyd Austin, head of U.S. Central Command, would make that recommendation to Obama if they determine Iraqis need U.S. help and there is no other option for providing it.

The official declined to be named due to the sensitivity of the situation but has direct knowledge of both generals' thinking.

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