The American Red Cross, subject of a wide-ranging investigation by the Food and Drug Administration over the safety of its blood supply, is expected to announce today that it is nationalizing the operations of its 54 regions and has replaced its national director of blood services.

Calling the changes "the most significant overhaul in Red Cross history," spokesman Brian Ruberry said the former blood service director, Lewellys F. Barker, has retired and will be replaced by one of the Red Cross's regional directors, whom he declined to name. The new director will report directly to Chairman George F. Moody, Ruberry said, and will have more authority over Red Cross centers and regional offices than Barker.

Other shifts in senior management also will be announced at a news conference by Moody, a volunteer and a chief executive officer of a Los Angeles banking corporation. "There will be some new positions and some people leaving," Ruberry said. Also, the agency's regions, which have been operating "rather independently," will be centralized in the Washington headquarters, he said.

The Red Cross board of directors decided at a meeting Wednesday that the changes were necessary "to ensure a safer blood supply and to better meet FDA standards," Ruberry said. He said that in addition to issues raised by the FDA, "we've been uncovering problems on our own in a number of regions."

The Red Cross supplies blood to more than half the hospitals in the country.

Dr. Joe Bove, director of the blood bank at Yale-New Haven Hospital and a specialist on blood supply issues, said it is hard to assess the significance of the changes. He said all regional blood banks had the same procedures and practices. "I'm not sure how much independence each of the regions had, so it is difficult to say how much independence each of them will be giving up."

A preliminary report on an FDA inspection of the Red Cross's national headquarters in Washington in May found that for years, various Red Cross regional offices had not reported accidents and errors made in the gathering and distribution of blood. Even when regions did make such reports, the audit found, Washington headquarters did not always review or follow up those reports.

One example the investigation cited concerned the Washington regional center. About 230 cases were reported to the Washington region in which people may have contracted the AIDS virus through blood transfusions, the report said, but headquarters was alerted to only four of those cases.

FDA officials said Red Cross procedures were not responsible for the infections. Almost all of the transfusions, they said, took place before 1985, when reliable AIDS tests became available.

FDA spokesman Jeff Nesbit said the agency was unaware of the pending changes. But "if they're putting in a system where they can get reports from their field office, that's all to the good," he said. Nesbit said the FDA "has an ongoing discussion with the Red Cross" and "I suspect those discussions will continue."

Staff writer Keith Harriston contributed to this report.