Leading senators expressed concern Sunday about a report that the CIA (search) has secretly moved as many as a dozen unidentified prisoners out of Iraq (search) in the past six months, a possible violation of international treaties.

Sen. John McCain said interrogations can help extract crucial information from detainees on plans for attacks against Americans. But international law, including the Geneva Conventions (search), must be followed, he said.

"These conventions and these rules are in place for a reason because you get on a slippery slope and you don't know where to get off," McCain, R-Ariz., told a Sunday morning network news show. 

"The thing that separates us from the enemy is our respect for human rights," he said.

Sen. Joseph Biden, D-Del., called for new leadership at the Justice Department.

The detainees were removed without notification to the International Red Cross (search), congressional oversight committees, the Defense Department or CIA investigators, The Washington Post said in Sunday editions, citing unidentified government officials.

The Justice Department drafted a memo dated March 19, 2004, authorizing the CIA to take prisoners out of Iraq for interrogation, according to the report.

Iraqis can be taken out of the country for a "brief but not indefinite period," and that "illegal aliens" can be removed permanently under "local immigration law," the newspaper quoted the memo as saying.

The transfers could violate the Geneva Conventions, which do not allow "individual or mass forcible transfers, as well as deportations of protected persons from occupied territory."

White House spokesman Sean McCormick said the U.S. policy is to comply with the international treaty, which protects civilians during war and occupation.

The Bush administration did not consider Al Qaeda (search) fighters in Afghanistan to be "protected persons" under the Geneva Conventions. Many were sent to Guantanamo Bay, Cuba, for interrogation.