"All the gains we have achieved in Iraq are now at risk," McCain said in an interview with the conservative think tank the American Enterprise Institute. "The enormous expenditure of blood and treasure that those gains entailed are now in jeopardy of being viewed by history as sacrifices made in vain.”

McCain, who famously said in his campaign for the presidency in 2008 that the Iraq war could go on for more than 100 years, said in Thursday's interview that the withdrawal from Iraq was one campaign promise the administration had, regrettably, managed to keep.

"For the past five years, the president has been completely consistent about his position on Iraq," said McCain. “[H]e constantly pledged to withdraw all U.S. troops at the earliest possible date. 

"Perhaps it should also not come as a surprise that the White House is now putting out glossy literature proclaiming that the president has fulfilled his campaign promise to withdraw from Iraq." 

Since the withdrawal of most U.S. troops earlier in the month, Iraq has descended into a state of instability not seen since much earlier in the war. Insurgents have carried out coordinated bombings across the nation's capital and a political crisis leaves Iraq's vice president hiding in the semi-independent region of Kurdistan.