The U.S. Supreme Court ruled yesterday that part of an FBI affidavit involving the disappearance of 5-year-old Melissa Brannen will remain sealed for as long as 10 weeks, virtually eliminating the chance it will be made public before the conclusion of Caleb Daniel Hughes's trial.

Hughes, a 24-year-old groundskeeper, is scheduled for trial Jan. 28 in Fairfax County Circuit Court, where a grand jury charged him with abducting Melissa from a 1989 Christmas party at the Fairfax community center where he worked.

The Supreme Court decision gives Peter D. Greenspun, Hughes's attorney, until early April to file a brief explaining why the court should hear arguments on whether the complete affidavit should be made public, as requested by The Washington Post.

All but one paragraph of the affidavit was released several weeks ago after The Post argued that release of the information no longer compromised the Brannen investigation because Hughes already had been indicted.

The delay is in effect a victory for Greenspun, who had argued that information in the affidavit is so disturbing that if it were released before Hughes's trial, it would generate negative publicity and make empaneling 12 impartial jurors difficult.

"We're pleased that the court gave emergency consideration to our request. Now we'll have the opportunity to fully brief this matter," Greenspun said.

The delay also undermines decisions by the U.S. District Court in Alexandria and the 4th Circuit Court of Appeals in Richmond, both of which ordered that the entire affidavit be released before the Hughes trial.

A divided three-member panel of the 4th Circuit agreed with U.S. District Judge Albert V. Bryan Jr., who said that Hughes's attorneys would have ample opportunity during jury selection to weed out potential panelists who were prejudiced against Hughes.

Circuit Judge J. Harvie Wilkinson III, in the appellate panel's Jan. 2 ruling, said, "The reason that fair trials can coexist with media coverage is because there are ways to minimize prejudice to defendants without withholding information from public view." Circuit Judge Hiram E. Widener Jr. dissented, saying the information could compromise Hughes's right to a fair trial.

Greenspun appealed the 4th Circuit opinion to Chief Justice William H. Rehnquist, who last week passed the request along to the full court.

U.S. Solicitor General Kenneth W. Starr filed an opinion with the Supreme Court that was interpreted by those familiar with the case as strongly supporting The Post's request for unsealing.

Starr said the application for a stay should be denied, arguing that the case "does not present any issue regarding the propriety of placing documents under seal" or challenge First Amendment or common law rights of access to court records.