The United States believes the increasing spate of hostage abductions in Iraq reflects a new strategy by a loose confederation of insurgents designed to increase public pressure on the U.S.-led multinational force and other foreign interests to abandon Iraq because bombings and other terrorist tactics have not had sufficient impact, according to U.S. officials.

U.S. officials said they detected a turning point in April when random abductions based on "targets of opportunity" and random access to foreigners evolved into a more regular and calculated pattern. Based on interviews with released former captives, Washington believes that many of those abducted end up in the hands of a fluid network of cells.

"We've seen this tactic now for several months, but it clearly took on the form of an established tactic six weeks to two months ago -- rather than a one-off or target-of-opportunity sort of thing," said a senior counterterrorism official familiar with the situation in Iraq.

About 90 foreign hostages have been abducted in recent months -- with about 60 since the April 8 abduction of three Japanese civilians, which U.S. officials mark as the turning point.

Various groups have claimed responsibility for the seizures. Followers of Abu Musab Zarqawi, a Jordanian extremist, this month claimed the abduction and execution of American Nicholas Berg and South Korean Kim Sun Il; another cell appears to be responsible for the kidnapping of Cpl. Wassef Ali Hassoun, a U.S. Marine not seen since June 19 and whose status was changed yesterday from missing to captured.

But as with the hostage abductions in Lebanon from 1982 to 1991, U.S. officials believe there are links among most of the abductors. "We have the impression now that there's a loose amalgamation where people can get picked up for any of a number of reasons and then enter an amorphous system that leads them to be handed off from one group to another and then they're evaluated for their value," said a senior counterterrorism official familiar with the Iraq kidnappings.

U.S. intelligence and counterterrorism officials are also investigating possible ties among the groups taking hostages in Iraq and Saudi Arabia, based on initial but sketchy information indicating the abductions are the work of extremists tied or sympathetic to al Qaeda and its allies.

"It's quite possible that there could be linkages," said a senior U.S. official tracking the trend. He noted that the Saudi group that seized and later beheaded American defense contractor Paul M. Johnson Jr. two weeks ago called itself the Fallujah Brigade of al Qaeda in the Arabian Peninsula. Fallujah is the Iraqi city at least partly controlled by militants who rose up against U.S. troops this spring.

Despite the transfer of political power in Iraq, the Bush administration is increasingly concerned about the abduction threat to Americans and allies. Kidnappers released a video Monday that appears to show the execution of Army Pfc. Keith M. Maupin, 20, who was captured April 9.

Hostage seizures are often more traumatic and enduring than any other terrorist tactic, U.S. officials said. "It's effective because it's a prolonged drama, unlike a terrorist event which is over after the bomb explodes or the bullet is fired and the bodies are taken away and the shattered glass is swept up and the buildings repaired. A hostage story takes on a life of its own. It's the apotheosis of terrorist theater," said Bruce Hoffman, a terrorism expert and director of Rand Corp.'s Washington office.

Taking hostages -- an age-old tactic used by Persians in the 6th century B.C., European rulers in the Middle Ages, Barbary pirates in the 19th century, and Latin American revolutionaries in the 1960s and 1970s -- can change the dynamics of political conflict by giving the weaker party a new edge, U.S. experts said. "Taking hostages brings them attention. It makes them appear to be potent players. It brings them recruits. It dismays their foes and makes their foes' lives untenable. And it creates political crises at home," terrorism expert Brian Jenkins said. "It's already brought about some withdrawals from Iraq and Saudi Arabia and created policy dilemmas for several governments. If we were cold-blooded analysts, we'd have to concede that it is in their view a good return on their investment."

Unlike in Lebanon, where Americans and other Western hostages were held as long as seven years mainly by Islamic extremists, the worst hostage dramas in Iraq have had more decisive and grisly endings. Some, such as the three Japanese in April and three Turkish hostages yesterday, were freed, but others have been beheaded -- to graphic effect.

"Terrorists don't even need the media as they once did to have impact. Technology has made it possible to put their savagery on their Web sites, which will be seen and onpassed," Hoffman said.

The United States has limited means of coping with hostage seizures or striking back. U.S. officials said they have some indications that other nations have negotiated with hostage takers or intermediaries, as happened in Lebanon in the 1980s and Latin America in the 1970s.

U.S. policy allows negotiations with hostage takers, but no concessions, leaving few options, a State Department official said.

"We hope that the world community will reject this tactic as extraordinarily inhumane and brutal so there'll be a consensus that this crosses beyond any reasonable standard of behavior," the counterterrorism official said. "If it's devalued, then you hope that people who have any information that can help resolve and return these people will be motivated to tell the authorities."

Researcher Robert E. Thomason contributed to this report.