US President Donald Trump's son-in-law, Jared Kushner, is in Baghdad to meet Iraqi leaders and be briefed on the fight against the Islamic State group.
Mr Kushner, the president's senior adviser, joined US Joint Chiefs of Staff chairman General Joseph Dunford.
The Marine general said he invited Mr Kushner to hear about the situation on the ground "first-hand and unfiltered".
He was also travelling on behalf of the president to express his support for Iraq's government, a spokesman said.
Navy Captain Greg Hicks, Mr Dunford's spokesman, said during meetings with Iraqi officials 36-year-old Mr Kushner would affirm US commitment to the fight against IS.
Kushner's limitless portfolio - Analysis, by Anthony Zurcher, BBC News
The Jared Kushner show has hit the road with a surprise visit to Iraq. It's the kind of unannounced trip that presidents and senior officials often make to show support for US troops overseas. This is something different, however.
Donald Trump hasn't been to Iraq yet. Neither has Secretary of State Rex Tillerson. Mr Kushner clearly has become the president's trusted eyes and ears in Washington and around the world.
He is a man with a nearly limitless portfolio. Delicate foreign affairs matters, business-friendly government reform, improving services for veterans and solving the opioid addiction crises are all items on his to-do list.
Is Mr Kushner up to such a tall task, given that his public office experience can be measured in weeks? The president seems to think so - which sheds light Mr Trump's governing philosophy.
The problems facing the nation are easy to solve, he seems to believe. The only reason they haven't been fixed yet is because the political establishment is either too corrupt or too incompetent. With Donald Trump overseeing the operation, however, a bright young man like Mr Kushner can parachute in and set things right.
We'll soon find out if the president right.
Gen Dunford on Monday also said he extended the invite weeks ago to Mr Kushner and Tom Bossert, the president's homeland security adviser, to help them gain insight into the war.
"I said, 'Hey, next time I go to Iraq, if you're interested, come and it'd be good,'" Gen Dunford said.
"The more appreciation you could have for what's actually happening on the ground, the more informed you are when you start talking about the strategic issues."
Mr Kushner, who is married to Mr Trump's daughter Ivanka Trump, declined to speak to reporters on the plane before his arrival in Iraq on Monday, Reuters news agency reported.
Mr Kushner's trip comes as Iraqi security forces are working to recapture Mosul, the last key IS stronghold in Iraq.
Nearly 290,000 people have fled the city in the wake of fighting, according to the United Nations.
Mr Kushner is expected later this week to attend meetings with Mr Trump and Chinese President Xi Jinping at the president's Mar-a-Lago estate in Florida.
Despite his lack of diplomatic, government or military experience, the 36-year-old has a busy schedule in the Trump administration.
The president last week picked him to lead a task force with a remit as wide-ranging as reforming federal bureaucracy and tackling opioid abuse.
Mr Kushner also serves as a shadow diplomat on US relations with the Middle East, Canada and Mexico.
Furthermore, Mr Trump assigned him the role of brokering a peace deal between Israel and the Palestinians.