United Steelworkers President Lloyd McBride conceded today his union may have made a "tactical blunder" in portraying its organizing struggle at the Newport News Shipbuilding and Dry Dock Co. as a potential breakthrough for the labor movement in the South.

At a press conference here in conjunction with the midwinter meeting of the AFL-CIO executive council, Mc-Bride said he would not be surprised if other corporations are putting pressure on Tenneco Inc., which owns the shipyard, to "stiffen up... don't give in."

Officials of the shipyard, which has 15,500 employes and is Virginia's largest private industry, have disputed the union's claims about the strike. Shipyard officials have said that 60 percent of the yard's workers are crossing picket lines and that the yard is able to meet its most urgent commitments.

Newport News Shipbuilding has yet to recognize the Steelworkers' victory at the yard and is engaged in a court fight over the issue.

Asked how he views the Newport News struggle in national terms, Mc-Bride said:

"We have perhaps made some tactical blunders in this respect, I'm not sure. Our union joined the groundswell of opinion that this was a struggle that went far beyond Newport News in its impace... I don't look upon it in that fashion at the moment. I look upon this as a struggle involving workers who are trying to get a contract from their employer that will result in improvements in their wages, hours and working conditions... We don't want to have our strikers involved in a strugle that goes beyond a contract covering them."

Noting that the union has a $90 million strike fund and just recently paid out nearly $400,000 as its first installment of weekly strike benefits to more than 13,000 workers, he said the Steelworkers are committed to continue supporting the strike as long as local members want.

In a resolution adopted yesterday and released today, the AFL-CIO Exexcutive Council pledged its support to the Newport News strikers and urged all affiliated unions to "provide whatever assistance may be necessary and legally permissable until the strike is won."