The mark was reached as Bush weighs options, including a short-term increase in forces of up to 30,000, to help control the deteriorating situation in Iraq where daily violence plagues Baghdad and much of the country.
Lieutenant-Colonel Mark Ballesteros, the Pentagon spokesman, said: "Every loss is regretted and there is no special significance to the overall number of casualties."
On Sunday, Bush, at his ranch in Crawford, Texas, mourned the death of the 3,000th US soldier, the White House said, but cautioned war-weary Americans that no quick end was in sight to the fight against terrorism.
The execution of Saddam Hussein has done little to help stem the sectarian violence tearing the country apart.
Armed groups killed at least seven people, including three Iraqi soldiers, a day after his hanging.
On Sunday, a group of armed in vehicles attacked an Iraqi army checkpoint in Hawijah, west of the northern oil hub of Kirkuk, killing three soldiers and wounding another two, local police said.
Four more people were killed in several attacks in Baghdad.
Two were killed and another two wounded when an armed group fired a Katyusha rocket in the capital's northwest Shia district of Kadhimiyah where Saddam was hanged.
Another Iraqi was killed and six others wounded in a car bomb attack in the northern neighbourhood of Hurriyah, a day after 37 people died in a triple car bomb attack in the same area.
In yet another attack, one person was killed and five wounded in a car bomb explosion in the Shawaqha neighbourhood in Baghdad.
On Saturday, car bombs killed more than 70 people in Baghdad and near Najaf, in areas populated by Shia Muslims.