Gen. William C. Westmoreland, describing himself as "an old soldier who loves his country," filed a $120 million libel suit yesterday against CBS Inc., contending that a controversial network broadcast falsely accused him of deliberately underestimating enemy troop strength in Vietnam.

Westmoreland said that despite the urging of family and friends that he "ignore CBS and leave the field," he decided to take the fight to court because "there is no way left for me to clear my name, my honor and the honor of the military."

Standing stiffly before a bank of microphones at the Army & Navy Club, Westmoreland said, "It was my fate to serve for over four years as senior American commander in the most unpopular war this country ever fought. I have been reviled, burned in effigy, spat upon. Neither I, nor my wife, nor my family want me to go to battle once again."

But he added that as he thought about the suit against CBS, which he described as a formidable and wealthy adversary, "I thought too of the troops I commanded and sent to battle, and those who never returned."

As the 68-year-old general, now retired, addressed reporters, his 15-page lawsuit was filed for him in federal court in his home state of South Carolina. Westmoreland said any damages that he wins from CBS will be donated to charities, including programs that benefit Vietnam veterans, soldiers on duty and the American Red Cross.

Van Gordon Sauter, the president of CBS News, said yesterday that the network "will mount a vigorous defense" against Westmoreland's lawsuit, which Sauter said is "devoid of merit" and "constitutes a serious threat to independent journalism in our society."

"We stand by the broadcast," Sauter said. After an internal investigation of the production last summer, which came after a critical TV Guide report on the program, and subsequent complaints from network affiliates, CBS defended its product. The network said, however, that there had been five violations of CBS news standards in the making of the 90-minute special report, entitled "The Uncounted Enemy: A Vietnam Deception."

In a prepared statement yesterday, Sauter said CBS still holds open an offer it made to Westmoreland last week of 15 minutes of unedited comment during a planned prime-time follow up to the January special report. Westmoreland, who last month unsuccessfully demanded a 45-minute on-the-air retraction, declined the offer of time on the follow-up. Broadcast of that program has been delayed.

Westmoreland contends that the CBS broadcast falsely and maliciously stated that Westmoreland and other senior U.S. military officials, in order to present a "rosier picture of the war than was the fact," suppressed and altered intelligence information about enemy troop buildup in the months before the 1968 Tet offensive by Vietcong and North Vietnamese forces, the heaviest offensive of the war.

Westmoreland alleges in the lawsuit that the CBS documentary, advertisements about the program, a preview interview about the broadcast and a CBS memorandum about the results of the internal investigation were intended to damage his professional reputation and portrayed him as "dishonest, unethical and ruthless."

In his court papers, Westmoreland also charges that language in program advertisements falsely and unfairly stated that there was a "conspiracy" to conceal information about enemy troop strength and that there was a "deliberate plot to fool the American public, the Congress and perhaps even the White House."

Days after the show was aired last January, Westmoreland held an emotional news conference, also at the Army & Navy Club, in which he called the production a "preposterous hoax" and accused CBS correspondent Mike Wallace -- now a defendant in the general's lawsuit -- of "premeditated malice."

In its internal study, CBS said that while it believed that the program showed "ample evidence of deception," the use of the word "conspiracy" was inappropriate. CBS, which refused to make public a 68-page report on the investigation, said in an eight-page statement that the program would have been a "better broadcast" if more persons who disagreed with the premise of the show had been interviewed. While there were violations of CBS news standards in the production, the statement said, they did not change the substance of the broadcast.

Westmoreland's lawsuit contends that CBS went ahead and published the advertisements, the preview interviews, the broadcast itself and the memorandum either knowing the material was false or with serious doubts about its truth, and with reckless disregard for the truth.

In addition to Wallace and Sauter, the lawsuit names as defendants the Columbia Broadcasting System, George Crile, the producer of the broadcast, and Samuel A. Adams, a former CIA analyst who was a consultant to Crile and was interviewed on the program.

Westmoreland is being represented in the suit at no cost by the Capital Legal Foundation, a conservative public-interest law firm based in Washington. Washington lawyer David M. Dorsen and attorneys in a South Carolina law firm will be paid by the foundation for their work on the case, according to Dan M. Burt, an attorney with the foundation.