Defense Secretary-designate John Tower's confirmation hearings expected to begin this week are likely to be the toughest and perhaps the longest of any accorded President Bush's Cabinet nominees.

"We're not going to play the `old boy go-around' with him this time," Senate Armed Services Committee Chairman Sam Nunn, D-Ga., said after Bush announced the former Texas senator as his choice for defense secretary.The committee, which Tower led as chairman when the Republicans controlled the Senate from 1981-85, tentatively scheduled the first of the hearings for Wednesday.

Unlike James Baker, who breezed through the Senate confirmation process to become secretary of state, Tower is expected to face tough questioning on a number of fronts - political, professional and perhaps personal.

Questions and rumors about Tower's professional and personal life have dogged the 63-year-old Texan since he was first mentioned as a candidate for the job he has sought for many years.

Tower served in the Senate for 23 years and, after leaving in January 1985, he worked as a consultant to many of the nation's biggest defense contractors. Critics contend these contacts do not inspire confidence in his promises to reform the Pentagon weapons procurement program.

Tower was also the subject of rumors about womanizing raised by his second wife in a bitter 1987 divorce and about excessive drinking. Tower has denied the allegations, and associates said he is only a moderate drinker.

Tower's appointment was announced Dec. 16 after a lengthy FBI background check that Bush said "totally satisfied" him that Tower was above reproach.

The FBI investigation "looked into a lot of rumors that proved to be groundless," and the report will "satisfy the most inquisitive members of the United States Senate," Bush said.

Nunn said that while he believes Tower to be well-qualified to be the nation's 17th secretary of defense, he wants to see the full FBI report.

Because of Senate etiquette, it is unlikely that questions about the rumors regarding womanizing and drinking will be raised in public by committee members. But Tower's consulting work is likely to be thoroughly examined.