The American Broadcasting Company cancelled yesterday's semifinals of the U.S. Boxing Championships and suspended future tournament bouts pending an investigation.

ABC, which is funding the tournament at a cost of $1.5 million, said the fights would be held up until the network could "guarantee the honesty and integrity of the tournament."

The U.S. Boxing Championships have come under fire the past several weeks by one fighter, Kenny Weldon of Houston, who claimed payoffs were required to compete, and by other fighters and persons in boxing who charged irregularities in the conduct of the event. A federal grand jury has been hearing some of the charges.

An ABC spokesman said yesterday's bouts in Miami Beach, Fla., were suspended after a fighter informed the network he had been told he could compete in the tournament and would be rated among the top 10 junior-middleweights in the country even though he had not fought for nearly two years.

The Washington Post learned that Ike Fluellen of the Houston suburb of Bellaire, Tex., also disclosed to ABC that the 1977 Ring Record Book credited him for victories in two 1976 bouts he never fought.

It was learned that Fluellen said the offer was made to him by Chris cline of District Heights, Md. Cline is a fight manager.

A federal grand jury has been hearing charges against the tournament promoters. Heavyweight Scott LeDoux contended after losing to Johnny Boudreaux at the U.S. Naval Academy on Feb. 13 that associates of promoter Don King controlled most of the boxers in the tournament, and that ring officials engaged by the tournament committee thus were biased against him.

The drastic step taken by ABC yesterday was one of the most significant acts involving boxing since the U.S. Supreme Court dissolved the International Boxing Club in 1959, ruling the promotional firm had a monopoly of champions, stadiums, and of which boxers would appear in televised bouts.

The U.S. Boxing Championships are being promoted by Don King Productions. The network filled in yesterday with boxing exhibitions by heavyweight champion Muhammad Ali.

The network issued a statement that said, in part, "Since the early stages of the tournament, ABC has been investigating various allegations of improprieties and has subsequently turned over to the U.S. attorney in Maryland evidence that it has uncovered such improprieties."

The network said it had further evidence indicating that several fighters appeared to have inaccurate records, which had been compiled by Ring magazine and used to determine the rankings of fighters entered in the tournament.

On Thursday, Nat Loubet and John Ort of Ring magazine announced their temporary withdrawal from the tournament committee while the boxers' records were being investigated.

The tournament is headed by James A. Farley, who also is chairman of the New York State Athletic Committee.

King said more than 30 ranked boxers had discrepancies in their records, and that 11 of them were among the 64 who began the tournament. He said four remain in competition, but refused to name them.

"This struck at the very heart of the championships because the fighters were picked according to the Ring magazine ratings," King said.

"We are trying to save the tournament by trying to stop the wrong-doers. I am the essence of the American dream, and I am not about to let something like this tarnish my reputation."

King said he agreed with ABC on the suspension of the bouts. "We have assisted ABC in the investigations and will continue to support any ongoing inquiry wholeheartedly and I welcome the appointment of a special investigator," he said.

"I hope to resume the tournament as quickly as the investigation is concluded."

The ABC spokesman said the inquiry would include a look at charges of kickbacks and other improper payments to intermediaries to get boxers into the tournament. Participation in the tournament was to have been on the basis of rankings.

The Associated Press quoted Ali as saying to King during the promoter's news conference in Miami Beach: "I don't know the mathematics of the problem, but I know your hands are clean and from what I can see of the problem here today, I believe, and they believe, that you're all right.

"There is only one thing wrong (with the tournament), Ali continued. "They got a black running it. We live in a white society and we're brainwashed to believing that white is right."

Featherweight Weldon touched off a controversy when he charged in an affidavit that he paid $200 in expenses and another $2,300 of his $7,500 purse to George Kanter of New York City to get into the tournament.

Tournament committee chairman Farley has described Kanter as primarily a booking agent for boxers. Kanter is not licensed as a manger.

Harlan Haas of Houston, acting as Weldon's representative, contacted Kanter for Weldon and said when the boxer made his payments public that Kanter was going to return the $2,300 to Weldon.

Farley also announced repayment would be forthcoming, but Weldon reported last week that he had engaged an attorney to try to collect from Kanter. The attorney, Lawrence Scroggins of Houston, said he was tired of trying to get Kanter to pay and had taken the case to the attorney for the New York State Athletic Commission.