Harry, 21, will serve in the Blues and Royals regiment of the venerable Household Cavalry, which already has been deployed to Iraq.
"It's fair to say that if his squadron goes to Iraq, he will probably go with it," a ministry spokesman said on condition of anonymity in line with ministry policy.
News reports said Harry hopes to lead an armored reconnaissance troop, which deploys in Scimitar vehicles and acts as the eyes and ears of the force commander.
There are two divisions within the Household Cavalry: the armored division, where Harry will train, and the mounted regiment, which performs ceremonial duties, including guarding the queen on ceremonial and public occasions.
Clarence House, the office of Harry's father, Prince Charles, said the young prince will join the Blues and Royals in April after completing his training at Sandhurst military academy in southern England.
Previous members of the Blues and Royals regiment include Andrew Parker Bowles, former husband of Charles' wife, Camilla.
James Hewitt, a former lover of Harry's mother, the late Princess Diana, also was in the Household Cavalry, but in the Life Guards rather than the Blues and Royals.
After being commissioned as an officer at Sandhurst, Harry will become a second lieutenant in the Household Cavalry.
Clarence House said the prince based his choice of the Blues and Royals "on the variety of roles which the regiment undertakes, including reconnaissance support to airborne forces right through to ceremonial duties."
Although Harry is keen to focus on operational work, the Household Cavalry has served in the Falklands, the Gulf, Bosnia, Kosovo and Northern Ireland, he may be required to take part in ceremonial duties.
However, he will escape sentry duty outside Buckingham Palace because he is an officer.
In an interview to mark his 21st birthday, Harry said he was keen to fight for his country.
"There's no way I'm going to put myself through Sandhurst and then sit ... back home while my boys are out fighting for their country," he said.
Harry is following a royal tradition by joining the military. Charles was a pilot with the Royal Air Force and Royal Navy, and Harry's grandfather, Prince Philip, had a distinguished career in the Royal Navy.
Harry's uncle, Prince Andrew, was a Royal Navy pilot and served in the Falklands war against Argentina.
Prince William, Harry's 23-year-old brother and second in line to the throne, currently is undergoing military training at Sandhurst.