The Bush administration continues to counter criticism of the Iraq war, using Friday, a U.S. field commander to argue that the job there is not yet done.

Colonel James Brown spoke by videophone with Pentagon reporters from a base north of Baghdad. He said the security of the United States depends on Iraq being made stable.

His appearance comes the day after a prominent Democrat called for the immediate withdrawal of U.S. forces from Iraq. Congressman John Murtha, a decorated military veteran, called the war "a flawed policy wrapped in illusion". He said the continued presence of U.S. troops in Iraq is a catalyst for violence.

The White House said it is "baffled" by Mr. Murtha's proposal.

The past week has seen a rapid exchange of harsh words between the administration and critics of the war, while surveys indicate public support for the conflict is dwindling.

Some information for this report provided by AP.