The United Steelworkers union has won another round in its legal battle to represent blue-collar workers at the huge Newport News Shipbuilding & Drydock Co. But the struggle may not yet be over.

In a ruling announced yesterday, the National Labor Relations Board upheld an administrative law judge's rejection of objections to a 1978 representation election that was won by the union.

The NLRB directed Newport News, the world's largest private shipyard, to begin bargaining for a contract with the union, but the company could delay further,if it chooses, by continuing litigation in the courts.

The Fourth U.S. Circuit Court of Appeals earlier this year rejected most of the company's allegations of impropriety but said there was enough doubt about whether illegal chain-ballot voting occurred to warrant further review by the NLRB. It was this review that was concluded by the board's ruling this week. A further review by the courts is possible, however.

A spokesman for the shipyard, which is a subsidiary of Tenneco Inc., a Houston-based conglomerate, said no decision has yet been made on whether to appeal the fourth Circuit ruling as reinforced by the NLRB decision.

The Peninsula Shipbuilders Association, the independent union that was ousted by the Steelworkers, could also appeal. It is said yesterday that it, too, was reviewing its options.

Noting that the company said earlier it would abide by the Fourth Circuit ruling, Steelworkers President Lloyd McBride called on the company to "honor that commitment" and come to the bargaining table.