UNITED NATIONS – An influential U.N.-appointed panel on Tuesday challenged the Bush administration’s right to use military force against an enemy that does not pose an imminent military threat.

The 16-member panel, appointed by U.N. Secretary General Kofi Annan after the U.S.-led invasion of Iraq, said in a long-awaited report that only the U.N. Security Council has the legal standing to authorize such a “preventive war.”

The findings reflect persistent international unease over the U.S. invasion without an explicit council endorsement, noting, “There is little evident international acceptance of the idea of security being best preserved by a balance of power, or by any single – even benignly motivated – superpower.”

It recommends the establishment of five guidelines that must be met before force can be legitimately used, including a determination that force is used as a last resort and that the threat is serious.

“There are good arguments for preventive military action, with good evidence to support them, they should be put to the Security Council,” the report said. But “in a world full of perceived potential threats, the risk of the global order … is simply too great for the legality of unilateral preventive action … to be accepted.”

Ric Grenell, spokesman to the U.S. mission to the United Nations, said the Bush administration would withhold comment until the report is formally released Thursday, noting, “We will review this report with an eye towards how, if at all, the recommendations will improve the workings of the Security Council.”

The 95-page report calls on states to define and aggressively confront terrorism, eradicate poverty that fuels extremism, and enlarge the U.N. Security Council to extend the influence of the world’s emerging powers.

It also urges the 15-nation council to refer cases of genocide and large-scale war crimes to the International Criminal Court, a recommendation expected to engender fierce U.S. opposition.

The report endorses the “emerging norm” that the Security Council has an obligation to intervene militarily “as a last resort” to prevent genocide, ethnic cleansing and other cases of mass killing that governments “have proved powerless or unwilling to prevent.”