The United States has more troops in Iraq now than at any previous time in the war, with around 162,000 members of the military in the country.
Pentagon spokesman Bryan Whitman said yesterday that the figure was due in part to handovers between units. As part of regular rotations, new US units work alongside those they are replacing for a time.
Whitman said that, while troop levels often fluctuated, the previous high was generally considered to be just over 161,000 in January 2005, when Iraq held national elections.
As part of a plan announced by President George W. Bush in January, the US has added 30,000 troops to its forces in Iraq - a measure known as the "surge".
Whitman said the regular level of US forces, including troops involved in the surge, would be around 156,000 or 157,000 if no units were moving in or out.
He said the rise above 160,000 was not due to any effort to increase the surge, which is highly controversial in Washington.
Democrats and some members of Bush's Republican Party have argued it is time to pull the troops out.
"There is no change to the level of effort and the combat power that we are projecting into Iraq," Whitman said.
More than 3680 US troops have died since US-led forces invaded in 2003 and toppled Saddam Hussein.
Meanwhile, the US and Britain yesterday pushed for a greater United Nations role in Iraq.
They introduced a resolution charging the UN with trying to bring together Iraq's embattled factions.
The resolution, expected to be approved tomorrow by the 15-nation Security Council, would upgrade the mandate of the UN Assistance Mission for Iraq and make it include promoting dialogue between Iraq and its neighbours.