WASHINGTON (AP) — The White House is declining to explain its criteria for directing drone attacks against American citizens working abroad with terrorists.

A newly disclosed Justice Department memo says the administration doesn't need evidence of a pending attack. The document says only that the target must be involved in ongoing plotting against the United States.

White House spokesman Jay Carney wouldn't discuss the memo in detail. He said President Barack Obama takes seriously his responsibility to protect the United States and its citizens. Carney said drone strikes are legal and that great care is taken to avoid the loss of innocent lives.