A federal appeals court halted Oliver North's Iran-Contra trial Thursday because of national security concerns after a jury was chosen to decide the fate of the fired White House aide.

U.S. District Judge Gerhard A. Gesell announced in court that "an administrative stay has been entered" by a panel of the U.S. Circuit Court of Appeals.The panel was pulling papers together, with a further ruling possible later in the day, Gesell said.

The administrative stay resulted from an attempt by the Justice Department to stop the proceedings out of concern that more stringent controls should be placed on North's plans to produce extensive amounts of classified material in his defense.

Minutes after the jury of nine woman and three men, all of them black, and six alternates were chosen, Gesell declared his intention to permit the prosecution to begin opening arguments.

After a brief recess, Gesell returned and disclosed the appeals court's action.

Earlier, Gesell had denied a motion by the Justice Department for a stay of the trial pending the outcome of its appeal seeking to have more stringent controls on classified material that North plans to present in his defense.

In denying the motion, Gesell said "The attorney general's belated general appearance is wholly misplaced. . . . The attorney general's attempt to appeal is . . . at odds with the purposes of the laws establishing the independent counsel," who is prosecuting the case.

Ron Noble, a Justice Department deputy to criminal division chief Ed Dennis, immediately went to the U.S. Court of Appeals in an attempt to get the trial stopped.

Gesell said he would check with the appeals court "and ask whether any instructions await me."

At issue is whether national security will be threatened by disclosure of classified information during North's trial on charges of shredding evidence and lying to Congress in an attempt to cover up the Iran-Contra affair.

The Justice Department stepped into the case Wednesday by demanding censorship control over classified documents that the defense wants to enter as evidence. That position was also opposed by independent counsel Lawrence Walsh, who is prosecuting North, a former White House national security aide.

The judge called the department's intervention in the case "one of the most frivolous motions I have ever seen."

Gesell said the only person who may make an appeal in the case is the independent counsel, but Noble responded that "the government's position is that the right to appeal is the attorney general's."

In a written order denying the stay, Gesell wrote that the Ethics in Government Act places all investigative and prosecutorial functions in the "exclusive control" of Walsh. "Independent counsel Walsh opposes the motion," he noted.