A senior State Department official said they were not aware of any Americans among the dead.
The cause of the stampede that happened in Mina, a large valley about three miles from Mecca, is unclear. However, it is not the first incident of this type, as millions of people push their way forward to get close to the walls.
The head of Iran's hajj organization, Saeed Ohadi, has blamed Saudi "mismanagement," telling state TV that the incident might have been caused by the closure of a road.
In 2006, more than 360 were killed in a stampede in the same area and another one occurred in 2004 leaving 244 dead and hundreds injured.
More than 160,000 tents are located in Mina, which is also the location where pilgrims throw pebbles and stones at the walls in a symbolic act of stoning of the devil.
In a statement released by the White House, a National Security Council spokesman said, "The United States expresses its deepest condolences to the families of the hundreds of Hajj pilgrims killed and hundreds more injured in the heartbreaking stampede in Mina, Kingdom of Saudi Arabia. Our thoughts are with them and the more than two million people undertaking the Hajj this year. As Muslims around the world continue to celebrate Eid al-Adha, we join you in mourning the tragic loss of these faithful pilgrims."
The Department of Justice added, "We are deeply saddened by the tragedy that took place in Mina, Saudi Arabia today during the holy Hajj pilgrimage, resulting in the death of over 700 people. Our thoughts and prayers go out to the families of the deceased and injured, as well as to the people of Saudi Arabia and other countries whose citizens died or were injured. At this time, during the blessed holiday of Eid al-Adha, the United States stands in support of Muslims around the world in the wake of this terrible tragedy."
The accident comes less than two weeks after a construction crane killed scores at the Grand Mosque in Mecca.