The Reagan administration has decided to impose limited sanctions against a British engineering firm when six turbines it made in Britain with U.S. components are shipped to the Soviet Union for use in the natural gas pipeline from Siberia to Western Europe, senior officials said today.

The first of the six turbines manufactured in Britain by John Brown Engineering Ltd. with U.S.-made rotors were loaded onto a Soviet freighter in Glasgow, Scotland, today in defiance of President Reagan's anti-pipeline embargo. U.S. officials said the administration is likely to act against John Brown when the ship sails later this week.

But the senior officials said John Brown would be blacklisted only from importing U.S. oil and gas equipment and technology. This would allow the diversified British company to import other American goods and services, including much of what is manufactured by various engineering subsidiaries owned by John Brown in the United States.

While the officials said the administration has set its course of action, White House deputy press secretary Larry Speakes told reporters here during Reagan's California vacation:

"No final decisions have been made. . . . The president has given some direction, but I think we will wait until the shipping takes place and at that time we will make a final judgment about the type of penalties we could impose."

The administration imposed sanctions last week against two French firms -- one a subsidiary of Dresser Industries of Dallas -- after Dresser France shipped three natural gas compressors to the Soviet Union for use on the pipeline.

Dresser France and Creusot-Loire, a French government-owned industrial giant, were prohibited from importing U.S. goods, services or technology until further notice.

Because nearly everything that Dresser of Dallas has exported to Dresser France involves oil and gas technology, the more limited sanctions that the administration has decided to impose against John Brown would be similar. But they would be significantly less damaging to the more diversified British firm.

Administration officials here and in Washington acknowledged that sanctions that hurt John Brown less than Dresser and the French firms are likely to provoke further adverse reaction from the French government and Dresser. "We're exploring ways" to see if the sanctions against Dresser and Creusot-Loire can be modified, one official said.

Administration officials said Reagan is adamant about enforcing the anti-pipeline embargo that he imposed following imposition of martial law in Poland. But the State and Commerce departments, sensitive to growing European resentment of the embargo, have urged that Reagan limit sanctions against John Brown.

Speakes said Secretary of State George P. Shultz and Secretary of Commerce Malcolm Baldrige discussed this today with national security adviser William P. Clark, who is coordinating foreign policy communications with Reagan during the president's vacation at his secluded ranch in the Santa Ynez Mountains northwest of here. But Speakes denied a report that they had spoken directly to Reagan earlier.

In Washington, State Department spokesman John Hughes reiterated the contention that Reagan's primary aim is putting pressure on Moscow to permit an easing of martial law in Poland, although other administration officials have long opposed the pipeline because of the economic benefit to the Soviet Union of selling large amounts of natural gas to Western European customers for hard currency.

Reagan's embargo also reduces benefits from the project, however, for firms in Western Europe and the United States that were involved in the pipeline's construction.

"While we have regret for the hardships or difficulties it might cause in Western Europe , the president is committed to his feeling," Hughes said. "He is very disturbed by what is happening in Poland. The fact that we ourselves may suffer from the situation underlines the the depth of that feeling."

U.S. Trade Representative William E. Brock conceded to reporters today that the embargo threatens to cause "substantial disarray" in U.S. political and economic relations with Western Europe.

He added that it showed the need for North Atlantic Treaty Organization members to focus on "whether we should continue to subsidize the Soviet Union" or seek "to reduce the amount of really strategic material" the Soviets are able to obtain from the West.

Administration officials have suggested that some overall agreement and action by the United States and its European allies on these questions could make possible a modification of Reagan's stance on the pipeline, but they and European officials said no progress has been made in continuing transatlantic consultations.

Brock sought to play down suggestions that a long-scheduled trip he will make to Britain later this week is intended to explore a solution to the problem, although he acknowledged that the pipeline is bound to be raised.

Other officials also said East-West trade could be a major issue at a scheduled meeting of NATO foreign ministers in Ottawa later this month if the pipeline conflict has not been resolved.