United Steelworkers President Lloyd McBride warned yesterday that a quick end is not in sight to the three-day-old iron ore workers strike that has halted most iron production in the country.

But he said he doesn't expect the walkout by about 15,000 USW iron workers to jeopardize the union pioneered no-strike agreement over national contract issues. Industry officials charge that the strike violates that agreement and could trigger its demise.

In remarks to the Washington Press Club, McBride said the steel industry has no incentive to resolve the dispute quick because of huge ore stockpiles but said it will do so when the "climate" is right.

Asked when that might be, he said, "Your guess is as good as mine." He said he doewn't not expect a settlement in "just a matter of a few days."

Denying industry contentions that the disputed matter - incentive pay for increased production - is a national contract issue. McBride reaffirmed the union position that it is a local issue not subject to the no-strike clause. He said "feelings are running high" on the issue. "Strikes are often easier to start than to end," he said.

The strike, which began Monday, is the first major work stoppage in the steel industry since a protracted industrywide walkout in 1959. The ore workers' dispute has shut down at least two-thirds of the nation's iron production, which is centered in Minesota and Michigan. Contracts covering most of the rest of the 1.1 million-member union have been negotiated.

McBride said he not currently involved in the negotiations because they are essentially local in nature but said he may enter the talks if the strike persists.

On other matters in a wide-ranging discussion of labor, economics and politics, the newly installed Steel-workers president said he:

Understands from union sources that the Labor Department has turned up insufficient evidence of voting irregularities to sustain a challenge to his election by his rival for the presidency, Edward Sadlowski.

Believes the steel industry should be able to charge prices sufficiently high to permit plant modernization and expansion.

Plans to support challengers to members of Congress who go back on promises to support labor-backed issues such as construction-site picketing and minimum-wage increases.

Thinks President Carter's performance has been "in balance not bad" and believes he could turn out to be a "great President."

Feels "comfortable" with George Meany as president of the AFL-CIO but won't commit himself to support re-election of the 82-year-old labor leader until he can assess Meany's well-being at the federation's December convention.

Rejects suggestions that the USW might try to take over the trouble-plagued United Mine Workers, telling a group of reporters before his speech that "we're not looking for new problems."