SANTA BARBARA, CALIF., NOV. 25 -- Presidential spokesman Marlin Fitzwater said today the White House has "no objection" to a Senate confirmation hearing at which the president's new national security adviser is asked about the Iran-contra affair and whether an active-duty military officer should hold the post.

Reagan has selected Army Lt. Gen. Colin L. Powell as his national security adviser but the White House has said Powell is to remain "acting" national security adviser until the Senate approves his military promotion.

Arnold Punaro, staff director of the Senate Armed Services Committee, chaired by Sen. Sam Nunn (D-Ga.), said today that Nunn and ranking minority member Sen. John W. Warner (R-Va.) have not decided whether to conduct the hearing. Previously, White House officials said they believed Nunn would call the session.

Nunn was a member of the Iran-contra committee, which recommended in its final report that the national security adviser should not be an active-duty military officer "as a matter of policy."

Fitzwater's comments welcoming a hearing at which Powell is questioned came as he also released a statement describing Powell's military promotion.

The statement said Powell "has the permanent rank of major general (two stars). He was confirmed by the Senate to temporary lieutenant general (three stars) when he assumed command of V Corps in 1986. The Senate reconfirmed him without a hearing as a lieutenant general when he became the deputy national security adviser. The president has requested the Senate to reconfirm his lieutenant general rank as he assumes his new position as national security adviser. As with any other military confirmation action, the Senate Armed Services committee may decide to hold a hearing."

Powell had moved up when Frank C. Carlucci was nominated as secretary of defense to replace Caspar W. Weinberger, who resigned after almost seven years.