Possible informants viewed in Iraq deaths

, Iraq, Aug. 5 (UPI) -- The deaths of more than 20 U.S. Marines in Iraq in two days have some wondering if there are informants among the Iraqi police ranks.

The Pentagon has admitted such infiltration exists, ABC said Friday, but experts warn it is hard to prove.

"There is no question that the war in Iraq involves serious problems with infiltration at virtually every level," said Anthony Cordesman, a military analyst for ABC News.

But, he added, there is no way to guarantee absolute loyalty among the 173,000 personnel in the military, security and police forces and the large mix of civilian bureaucrats and contractors.

The Pentagon expressed those concerns July 21 to Congress in a report saying that the Iraqi "Commando" and "Special Forces" are improving, but that border control units remain weak, with a high level of infiltration by insurgent groups.