Treasury Secretary Donald T. Regan said yesterday the Reagan administration would soften the sanctions it imposed last week against two French companies -- one a subsidiary of Dresser Industries of Dallas -- for shipping equipment to the Soviet Union for its natural gas pipeline to Europe.

Regan said the U.S. government's blacklisting of the two firms -- Dresser France and the French government-owned Creusot-Loire -- would be modified to match a more limited ban on trade in oil and gas technology that will be imposed on a British firm, John Brown Engineering Ltd., for also violating Reagan's anti-pipeline embargo.

Calling this a "clarification" or "redefinition" rather than a "rollback" of the sanctions against the French firms, Regan told reporters, however, that "perhaps in its original form [the blacklisting] was a little too sweeping without giving any definition of what was meant."

The more limited sanctions would bar the French and British companies only from importing American oil and gas equipment and technology, allowing them to continue other trade with American firms. Regan said similar limited sanctions would be imposed against other firms in Europe that violate Reagan's embargo against any use of U.S. technology in the pipeline.

Commerce Secretary Malcolm Baldrige said in a television interview earlier yesterday that "we're not going to back away from sanctions, but we have to make sure those sanctions are directed at what we think the essential problem is -- the Polish problem."

But one middle-level official outside the Treasury Department cautioned that Regan was speaking "for himself" and not necessarily for President Reagan. Several Cabinet members have urged the president through aides to ease the sanctions, which have caused growing resentment among U.S. allies in western Europe and among American firms affected adversely. Others inside the administration, however, have been advocating a continuing tough response to embargo violations.

"There is an attempt under way to stampede and flummox the president into a position he doesn't want to take," the official said. He cautioned that Tuesday's demonstrations in Poland could play a part in what happens next, suggesting that it might be bad timing for the administration to relax sanctions the day after the Solidarity anniversary demonstrations.

"You have to keep an even hand," Regan said at a press conference yesterday. "Let's remember what this is all about, let's go back to square one. This has to do with the Polish situation. Now all of you are reading the headlines, the same as I am. The Polish situation has not improved. Therefore, we believe that our sanctions agains the Russians are justified.

"Our sanctions are designed against the pipeline, which will bring gas from Siberia into Western Europe. Our sanctions have to do with oil and gas -- they certainly wouldn't involve, let's say, IBM typewriters, say against Olivetti typewriters being purchased by Dresser France, or what have you. So it relates to oil and gas equipment."

Regan said the modification of the American response in what has become a bitter economic tug of war between the U.S. and its closest allies will become apparent when a Soviet freighter, loaded with six turbines manufactured in Britain by John Brown Engineering Ltd., moves out of the port of Glasgow, Scotland. Another American official said the president might not act for a few days "to let the dust settle."