The U.S. missile attack launched from a Predator drone aircraft that killed six suspected al Qaeda terrorists traveling in a vehicle in Yemen on Sunday was carried out with the cooperation and approval of that country's leadership, U.S. sources said yesterday.

An administration official with knowledge of the attack said the CIA-controlled Predator was being operated under a presidential finding that authorized covert actions by the agency against Osama bin Laden's terrorist organization, and although civilians were killed in the attack it was considered a military action and not an assassination.

Nevertheless, the attack has touched off a new debate on whether the United States -- with or without the assistance of friendly foreign governments -- should attack suspected terrorists outside of military zones.

Current and former government officials said the Yemen attack illustrates that the war on terrorism requires new rules for fighting. The sources emphasized that the Bush administration expects that future attacks would be carried out in cooperation with other governments, as was this one -- if sometimes secretly. White House press spokesman Ari Fleischer said, "The president has said very plainly to the American people that this is a war in which . . . sometimes there are going to be things that are done that the American people may never know about."

The remotely flown Predator fired a missile that obliterated the vehicle and its passengers. The administration official knowledgeable about the attack said the extraordinary damage -- the vehicle was blown up and the individuals were burned almost beyond recognition -- was caused by an "unexplained secondary explosion," which indicated the occupants were carrying arms, explosives or extra gasoline.

Yemeni officials privately told reporters in that country that their intelligence agents were watching and communicating to U.S. intelligence the movements of Abu Ali al-Harithi, the senior al Qaeda operative who was the primary target in the attack. The government of Yemeni President Ali Abdallah Salih has announced only that it is investigating the cause of the explosion, according to the country's official news service.

In the wake of the attack, however, a statement by Salih was read over Yemen national television, asking those who had joined bin Laden's network to come forward in order to avoid what happened to al-Harithi. "We call on everyone from among our countrymen who have been entangled in membership of the al Qaeda organization to repent . . . and renounce all means of violence," Salih's statement said.

State Department spokesman Richard Boucher declined to comment on any U.S. role in the attack.

Asked how the action in Yemen squares with past U.S. opposition to Israeli "targeted killing" of Palestinians, Boucher said, "If you look back at what we have said about targeted killings in the Israeli-Palestinian context, you will find that the reasons we have given do not necessarily apply in other circumstances."

While other senior officials declined to discuss the Yemen attack on the record, Deputy Defense Secretary Paul D. Wolfowitz appeared on CNN yesterday and called it "a very successful tactical operation." He said the attack had not only "gotten rid of somebody dangerous," but also "imposed changes in their tactics and operations and procedures." He added, "We have just got to keep the pressure on everywhere we're able to."

President Bush and Defense Secretary Donald H. Rumsfeld have repeatedly said that U.S. forces would take the offensive in seeking, capturing and, if necessary, killing al Qaeda forces wherever they are. Until now, however, those actions were primarily carried out by ground-based forces in the border area of Afghanistan and Pakistan. Although U.S. Special Forces units have recently been sent to Yemen, Georgia and other countries to train local troops in counterterrorist operations, Sunday's operation was the first in which a Predator -- a sophisticated surveillance and attack aircraft with a range of hundreds of miles -- was used to attack and kill suspected terrorists in another country. The Predator that was used in the attack reportedly is based in Djibouti, the small republic about 100 miles across the Gulf of Aden from Yemen.

Former senator Warren B. Rudman (R-N.H.), who chaired the President's Foreign Intelligence Advisory Board during the Clinton administration and co-chaired a recent presidential commission that examined homeland security, said the Yemen attack illustrated the administration's new policy. "I think in the war on terrorism there are no rules. They [the terrorists] have none and we have to take whatever risks you have to take to make them fear us."

He said he believed that as long as people have been identified by intelligence, the United States could carry out attacks within other countries even without the cooperation or approval of those governments.

A senior foreign policy adviser in the Clinton administration said that fighting a war against a "stateless terrorist enemy" requires working with friends and allies, but added: "We have to make sure that the U.S. government does not become -- in fact or perception -- judge, jury and executioner around the world. If the technique is used indiscriminately, there will be a backlash."

Sweden's foreign minister, Anna Lindh, traveling yesterday in Mexico, was the first foreign official to publicly criticize the Yemen attack. "If the U.S.A. is behind this with Yemen's consent, it is nevertheless a summary execution that violates human rights," she said. "Even terrorists must be treated according to international law. Otherwise, any country can start executing those whom they consider terrorists."