Former national security adviser John M. Poindexter testified yesterday that he firmly believed the National Security Council staff was exempt from congressional restrictions on U.S. military aid to the Nicaraguan contras and that the NSC staff had become a secret operational unit overseeing private support to the rebels.

Poindexter also said he kept President Reagan informed in "general terms" of the NSC's contra support activities.

Poindexter's testimony contradicted Robert C. McFarlane, his predecessor as national security adviser, who testified Tuesday that the two-year aid ban, known as the Boland Amendment, applied to the NSC staff.

Poindexter also contradicted Reagan's Jan. 26 statement to the Tower review board in which the president said he "did not know the NSC staff was engaged in helping the contras."

The rear admiral's testimony lined him up squarely with his former subordinate, Lt. Col. Oliver L. North, and against McFarlane in recounting what these key figures in the scandal say they believed was lawful conduct for the NSC at the time the Boland Amendment was in force.

On Tuesday, in an unusual return appearance before the congressional Iran-contra panels, McFarlane disputed North, saying, "It was very evident that the intent of Congress was that this {Boland} amendment applied to the NSC staff."

McFarlane, national security adviser when the amendent took effect in October 1984, recounted his efforts to have Congress change the legislation. "If we felt we were not covered, what was I doing . . . trying to get rid of it?"

However, Poindexter, who was McFarlane's deputy when the ban became law, testified yesterday that "I never believed that the Boland Amendment ever applied to the National Security Council staff or the president's personal staff."

Poindexter's testimony supported North, who testified that he considered his support of the contras legal because as an NSC staff member he was not covered by the Boland Amendment.

Poindexter also testified that he was under the impression that McFarlane, while national security adviser, had authorized North's activities on behalf of the contras. When he succeeded McFarlane, Poindexter said, he instructed North to continue the work.

The NSC staff "had been running this {contra support} operation on our own for a long period of time because there was no other alternative in order to keep the contras alive," Poindexter said. Before the ban, the Central Intelligence Agency, with assistance from the Defense and State departments, had provided military and other aid to the contras as part of the administration's efforts to oppose Nicaragua's leftist Sandinista government.

Poindexter said that during the ban on U.S. aid, Reagan told him, "I don't want to pull out our support for the contras for any reason.

"Isn't there something I could do unilaterally?" Poindexter quoted the president as saying.

Poindexter said he kept the president generally apprised of North's efforts to support the contras. "I did not get into the level of detail with {Reagan} as to exactly how Col. North was carrying out his charter to keep the contras alive," Poindexter said.

Poindexter said he told Reagan that a secret airstrip had been constructed in Costa Rica in connection with private efforts to support the contras. Other testimony has shown that North directed the building of the airfield as part of a private operation that he had helped set up to fly arms to the contras inside Nicaragua, and that the airstrip was built with funds diverted from the secret U.S.-Iran arms sales.

The contra resupply operation was exposed last October when one of its cargo planes was shot down over Nicaragua, leading to the capture of American Eugene Hasenfus. At the time, Secretary of State George P. Shultz and Assistant Secretary Elliott Abrams said there was no U.S. involvement with the downed plane -- statements they now acknowledge were inaccurate.

After the congressional hearings began, Reagan reversed himself and said he was "kept briefed" on private contra support. "I was very definitely involved in the decisions about support to the freedom fighters," Reagan said. "It was my idea to begin with."

@Linda Poindexter, left, listens to her husband's responses to questions posed by Senate chief counsel Arthur L. Liman, above. Copy of a memo, right, from then-CIA Director Casey asking Poindexter to have President Reagan sign an Iran arms-sale approval. Poindexter testified that he tore up the finding.