In a new memorandum released on Friday, the department stepped back from its August 2002 position that only the most severe types of torture were not permissible under US and international agreements.
The new memo was broader in its definition of what could be considered illegal, and therefore what was unacceptable under US law and under the United Nations Convention Against Torture.
In particular, the new memo disagrees with the previous statement that "severe" pain under the terror statute was limited to pain "equivalent in intensity to the pain accompanying serious physical injury, such as organ failure, impairment of bodily function, or even death".
The new document also disagreed that "severe" pain is limited to "excruciating and agonising" pain.
Acting Assistant Attorney-General Daniel Levin said in the new memo that torture may consist of acts that fall short of provoking excruciating and agonising pain and thus may include mere physical suffering or lasting mental anguish.
His opinion is meant, according to its language, to undermine any notion that those who conduct harmful interrogations may be exempt from prosecution.
Under international law, torture is defined as an act specifically intended to inflict severe physical or mental pain or suffering.