Media watchdog organizations have expressed shock and concern that reporters could be treated as "unprivileged belligerents" under the Defense Department's new Law of War Manual, which provides guidance for US commanders and others.

The Pentagon has insisted it "supports and respects the vital work that journalists perform." But some media advocates see too much room for maneuver in the guidelines.

Reporters Without Borders joined other organizations this past week in expressing concern, sending a letter to Defense Secretary Ashton Carter urging consultations on the issue.

In the letter to the US defense chief, the Paris-based group said it was concerned that journalists could lose "privileged" status in combat areas merely by "the relaying of information," which, according to the guidelines, "could constitute taking a direct part in hostilities."

"This terminology leaves too much room for interpretation, putting journalists in a dangerous situation," said the group's secretary general, Christophe Deloire, in the letter.