WASHINGTON  The Federal Bureau of Investigation has requested a last-minute delay in the release of a report on the bureau’s anthrax investigation by the National Academy of Sciences, prompting a congressman to say that the bureau “may be seeking to try to steer or otherwise pressure” the academy’s scientific panel “to reach a conclusion desired by the bureau.”

Representative Rush D. Holt, a Democrat of New Jersey and a physicist who has often been critical of the investigation, made the remarks in a letter Thursday to the F.B.I.’s director, Robert S. Mueller III, saying that he found the bureau’s request for a delay “disturbing.” The F.B.I. has told the committee that it wants to turn over an additional 500 pages of investigative documents not provided previously despite the committee’s request for all relevant material when it began the review in April 2009.

“If these new documents were relevant to the N.A.S.’s review why were they previously undisclosed and withheld?” Mr. Holt wrote. The anthrax-laced letters that killed five people in 2001 were sent from a mailbox in Princeton in his district.

Michael Kortan, an F.B.I. spokesman, declined to respond to Mr. Holt’s remarks. But he said, using the bureau’s name for the investigation, that the F.B.I. “continues to work with the National Academy of Sciences to support their ongoing review of the scientific approaches employed in the Amerithrax investigation.”