WASHINGTON: US President George W Bush has given his national intelligence director greater powers to manage rival US spy agencies as part of an overhaul driven by past intelligence failures, White House documents released show.

The authorities were spelled out in revised executive order 13355, which Bush signed, carrying out reforms enacted four years ago in the wake of intelligence fiascos involving Iraq and the September 11, 2001 attacks. "This is the first significant adjustment in the executive order in several decades," a senior administration official said, speaking on condition of anonymity. Officials said the new order released retains bans on assassinations of foreign leaders, limits on human experimentation, and protections of civil rights of US nationals contained in the original order, which was signed in 1981 by then president Ronald Reagan.

The most significant changes focus on the role of the director of national intelligence, or DNI, a post created under a 2004 law that took overall responsibility for US intelligence away from the Central Intelligence Agency. The CIA remains in charge of espionage under the revised order, which assigns the agency the role of "functional manager" for human intelligence.

The CIA also remains the one agency permitted to conduct covert actions, with the exceptions of the military in time of war or "unless the president determines that another agency is more likely to achieve a particular objective." But the director of national intelligence is responsible for overseeing and advising the president on all ongoing and proposed covert action programs under the revised order.