Defense Secretary-designate John Tower's nomination received a damaging blow when Sen. James Exon, D-Neb., said he will oppose it because a secret FBI report suggests Tower may not have beaten a drinking problem.

The Senate Armed Services Committee planned a closed afternoon session Thursday to decide when to vote on Tower's nomination. Exon's statement late Wednesday followed Chairman Sam Nunn's declaration that he disagrees with President Bush's claim the report knocks down allegations against Tower.But White House press secretary Marlin Fitzwater scoffed at Exon's comments, saying: "We disagree. If you want to believe gossip, then you can."

Nunn, D-Ga., and Sen. John Warner of Virginia, the senior Republican on the committee, spent nearly three hours Wednesday going over the report with committee members in a bug-proof vault atop the Capitol. Both senators said they had not made up their minds how to vote.

Exon's comments were the most glaring sign the 63-year-old former Texas senator's nomination could be in trouble, at least in the committee. But regardless of the committee vote - to recommend, reject or make no recommendation - Tower's nomination is expected to go to the full Senate next week.