General Martin Dempsey, chairman of the U.S. military's Joint Chiefs of Staff, has arrived in Iraq on an unannounced visit.
He arrived in Baghdad early on November 15.
It is Dempsey's first visit to Iraq since a U.S.-led coalition began a campaign of air strikes against Islamic State militants and other Islamist groups in Iraq and Syria.
Dempsey told Reuters he wanted to see how the U.S. "contribution is going."
The trip by Dempsey, a veteran of the Iraq war, comes two days after he told the U.S. Congress that the government would consider sendin a small number of American troops to fight with Iraqi forces when they are involved in more complex campaigns against IS fighters.
IS forces control large parts of northern and western Iraq and swaths of Syria.