Senator Rand Paul will introduce legislation Tuesday to finally bring Washington's Iraq war authorization to an end, his office said, and the White House backs the Republican's efforts in principle.

US forces withdrew from Iraq more than two years ago and President Barack Obama declared the war over, yet a loophole in the law green-lighting the March 2003 invasion of Iraq allows for future US presidents to send troops back to the turbulent country.

The bill by Paul, a libertarian who has consistently sought to scale back foreign intervention by US forces, would repeal the Authorization for the Use of Military Force (AUMF) in Iraq.

"The war in Iraq is officially over," Paul said, according to Foreign Policy magazine.

"With the practical side of the mission concluded, I feel it is appropriate to bring this conflict to an official, legal end."

Paul, a potential 2016 presidential candidate, has clashed with Obama on numerous national security issues, notably on the use of military drones, but the White House backs the senator's latest position.

"The administration supports the repeal of the Iraq AUMF since it is no longer used for any US government activities," National Security Council spokeswoman Caitlin Hayden said in a statement, laying out the White House stance first reported by Yahoo News.

"We understand that some in Congress are considering legislation related to the Iraq AUMF, and we will certainly examine these proposals as they come forward."

One US official said the White House has not actively sought to repeal the AUMF "because the effect would be entirely symbolic, and we have many more pressing priorities to take up with Congress."

By more than two to one, US lawmakers in October 2002 authorized president George W. Bush to use military force to oust Iraqi president Saddam Hussein. The legislation cited the need to seize control of Iraq's stockpile of chemical weapons and its nuclear program.

The resulting 2003 invasion has haunted US politics for years, with Bush administration claims, including Hussein's weapons of mass destruction and alleged links with terror network Al-Qaeda, widely discredited.