The U.S. Customs Service, faced with allegations that it conducts abusive searches of airline passengers in its attempts to capture drug smugglers, plans to announce today that it will seek the advice of U.S. attorneys when detaining travelers for more than eight hours.

The announcement, disclosed by a senior Customs official, appears likely to end a months-long effort by Customs Commissioner Raymond W. Kelly to change agency policy by setting up an outside review process to help ensure that the agency's inspectors have acted on "reasonable suspicion" when they detain travelers.

At most airports and other border crossings, Customs can detain passengers for lengthy periods--sometimes days--without court approval. The procedure, which has been upheld by the Supreme Court, helped fuel allegations in recent years that Customs wrongly targets blacks and Hispanics as suspected smugglers.

Three months ago, Kelly said he planned to require Customs to seek the approval of federal magistrates when detaining travelers for more than four hours. But sources said that plan encountered opposition at the Justice Department, which questioned which legal standard Customs would use to call on magistrates for such a ruling. Instead, the Justice Department agreed that U.S. attorneys could be used to provide an outside opinion on whether Customs acted on a reasonable suspicion when detaining a traveler.

Under reasonable suspicion, Customs may detain a person and ask for the traveler's consent to medically supervised body searches. If consent is not given, Customs may proceed with X-rays, physical exams and the monitoring of bowel movements. The strip searches and other tactics have drawn protests and criticism in lawsuits and on Capitol Hill.

Kelly, who took over at Customs last year, has tried to address many of the complaints by shaking up the agency's staff and tightening procedures. Customs, for example, has drafted a new "Personal Search Handbook" that provides updated guidelines for inspectors trying to detect drug smugglers. Under Kelly's new rules:

* A Customs supervisor must approve pat-down searches.

* Any travelers delayed for two hours must be given the opportunity to have a Customs officer notify family or friends.

* A senior Customs officer must approve all searches that require moving a traveler to a medical facility for a medical examination. The officer must consult with a Customs attorney on all medical exams.

* A Customs officer must explain the detention process to the person under suspicion.

In addition to these changes, Kelly has installed "body scan" machines at six major airports, including Los Angeles, Chicago and New York, to provide travelers with an alternative to strip searches. He also has requested $9 million to install X-ray machines at major airports to give travelers another option for a less intrusive body search.

Kelly also has appointed an independent commission to conduct a comprehensive study of Customs search policies and practices, including allegations that some Customs inspectors may have improperly used race as a criterion for ordering searches of travelers. Customs officials hope to receive the commission's findings before the year ends.