The French government announced July 22 that it had ordered a French engineering company to defy the United States embargo on the Soviet gas pipeline.

The company, Alsthom-Atlantic, now will go ahead and manufacture 40 gas-turbine rotors, which it produces under General Electric license.

The decision is crucial to the execution of the controversial multibillion dollar natural gas contract with the Soviet Union. Alsthom-Atlantic was the only European company with the ability to produce the needed turbines for the project. But to do this, it has to defy the American embargo.

The decision is likely to cool even further already chilly Franco-American relations. Earlier this week, US Ambassador Evan Galbraith warned once again that Alsthom-Atlantic would face fines and legal prosecution if it fulfilled the contract.

Such warnings made the French wait nearly a month since the technology embargo was first announced by President Reagan before deciding to go ahead. Officials at the French Foreign Ministry kept saying they hoped a compromise of some sort could have been worked out without an open break over the issue.

But evidently the French finally lost hope in reaching any deal with the Americans. French Foreign Minister Claude Cheysson July 21 spoke of ''a progressive divorce'' between Paris and Washington.

''We no longer speak the same language,'' he said. ''The United States seems totally indifferent to our problems.''

President Reagan declared an embargo on all American technology for the Soviet gas contract last June 18. The embargo promised to delay the construction of the contract for a year or two, primarily because it would stop Alsthom from constructing the needed turbines under American license.

The Americans fear that increased Russian gas sales to Western Europe will give the Soviets too much leverage over the allies. The Reagan administration also does not want the Soviet Union to receive needed hard currency from Europe.

As Ambassador Galbraith said July 21, ''We have decided it is not in the interest of the US to aid the Soviet Union in the augmentation of its production of natural gas.''

As a result, the French seem determined to show the US that it cannot bully them. In its statement announcing the decision, the French prime minister's office said, ''The French government cannot accept unilateral actions taken by the US.''