The official from the U.S. Office of Reconstruction and Humanitarian Assistance, speaking on condition of anonymity, said the new policy would help Iraq move on from the legacy of Saddam's regime. 

"The Baath Party in Iraq is finished," the official said. "We mean to be sure that by this process, we will put a stake in its heart." 

The reconstruction team's purging efforts, which the official said would begin within days, are the next step in the United States' vow to eliminate Baathism from postwar Iraq. 

Reconstruction officials in Iraq are trying to get the country's ministries and civil service working again, and are struggling to make sure they purge Saddam sympathizers without gutting the entire bureaucracy. 

"We are indeed serious. This is an indication of how serious we are," the official said. "It will come out right." 

As many as 1.5 million of Iraq's 24 million people belonged to the party under Saddam. But only about 25,000 to 50,000 were full-fledged members - the elite targeted by U.S. officials. Many Iraqi civil servants could obtain jobs only after making affiliations with the Baath Party. 

Friday's order, signed by U.S. civilian administrator L. Paul Bremer, intends to halt Baathists from the party's top four echelons from any public position - whether in universities, hospitals or minor government posts. 

An even stricter vetting process awaits officials appointed to Iraq's ministries dealing with security, such as the ministries of defense and interior. 

The reconstruction official said exceptions would be made in the winnowing process and also said all but 2,000 of the thousands of Baathists in question had melted away and were not angling for new government jobs. 

The ORHA official said Iraq's American overseers would comb through the deposed regime's records, interview suspected Baathists' co-workers and seek testimony to make sure the government is free of the party's influence. 

The official acknowledged the process would prevent some of the country's most able administrators from helping rebuild the country. 

"The de-Baathification will entail some inefficiencies in the running of the government," the official said. "That's the price we're willing to pay in order to extirpate Baathism from Iraqi society." 

Despite the ban, some former Baathists are bound to slip through, while innocents could be denounced by co-workers seeking revenge, the official said. 

This week, the interim head of the Health Ministry quit after drawing protests from doctors for his ties to the Baath regime. Dr. Ali Shenan al-Janabi, an optometrist, was the ministry's No. 3 man under Saddam. 

The U.S.-led administration, which earlier had praised al-Janabi, said it accepted his resignation "due to his refusal to condemn the Baath Party." 

Former Baathists are also fueling crime and anti-American unrest in Iraq while "trying to reorganize and reconstruct" the party, the official said. 

Any public displays supporting Saddam have also been banned by the U.S. occupying force, the official said, adding that rewards would be offered for the whereabouts of senior party officials. 

The order does not specifically ban gatherings of former Baathists, a move the official said could come later. 

Many of the upper-level figures in Saddam's regime - the most-wanted, including the Iraqi leader himself - are already being pursued after being depicted on a deck of cards designed to familiarize U.S. forces with their faces. 

The Baath Party was founded in neighboring Syria in 1943 and spread across the Arab world, promoting Arab superiority and Arab unity with a violent, Soviet-style party structure. 

Iraq's Baath Party, dominated by Sunni Muslims in a country that has a Shiite majority, took power briefly in the early 1960s, then ruled Iraq continuously from 1968 until last month - most of that time under Saddam. 

Neighboring Syria is ruled by a rival Baath faction headed by President Bashar Assad.