The nation's three largest steel companies disclosed yesterday that they are on the verge of filing formal complaints accusing Japanese and European steel makers of "dumping" steel in the United States.

The first of the dumping complaints will be ready to be filed by next week, the steel makers said. If found to be justified, the complaints would force the federal government to put tariffs on steel imports.

Government officials long have feared such an action by the steel industry could trigger an international trade war.

At the urging of the government the steel companies have held back from filing dumping complaints that could trigger tariffs, giving the Carter administration a chance to try to find other ways to deal with steel imports.

The U.S. steel industry has been complaining about competition from low priced imports for years and threatening to bring dumping cases for months, but have never before indicated they were close to filing the complaints.

The companies showed their hand yesterday at a press conference called to release an American Iron and Steel Institute study of the problems the industry faces in the decade ahead.

Warning that steel imports could rise, forcing U.S. companies to close more plants and lay off more workers, the industry renewed its call for government aid. Basically they're asking three things:

Liberalizing federal tax laws to allow them to write off the cost of new plants and equipment over a shorter period of time. That would save the companies millions of dollars a year and the money would be reinvested in steel-making facilities, the industry says.

Loosening federal pollution control regulations, to allow existing steel plants to continue to pollute and to let the companies build new plants that do not meet present air and water pollution standards. The Carter administration already has granted some concessions in this area.

Protecting the industry from import competition, by controlling either the quantity of steel imported into the U.S. or the price at which it is sold.

"In my judgment we have not made any meaningful progress in any of the three," said George A. Stinson, chairman of National Steel Corp., the number three steel maker. Stinson appeared along with Lewis W. Foy, chairman of number two Bethlehem Steel Corp., David Roderick, chairman of U.S. Steel Corp., the biggest in the business, and William H. Knoell, president of Cyclops Corp., the largest specialty steel maker.

Warning of the dangers of depending on foreign steel makers, Roderick said, "The bottom line is that sometime in the mid 1980's this country could have a very comparable situation to what is now going on in oil. Foreign countries would dictate what we pay for steel as they now dictate what we pay for oil."

Asked by a Japanese journalist if the companies were preparing dumping complaints, all those of the basic steel company executives answered affirmatively.

Roderick said U.S. Steel will have its case against steel imports from seven European steel making countries ready by next week and will have a case against Japanese imports ready within 60 days.

He said U.S. Steel is prepared to prove that European steel makers are selling steel in the U.S. for less than it costs them to make it and for less than they charge in their home countries.

Either practice would amount to "dumping" under U.S. trade laws. If the companies can document the charges, the Commerce Department could be forced to slap temporary duties on steel imports that would raise their prices.

If the steel companies can then prove they were harmed by unfair import competition, the International Trade Commission would be required to make the duties permanent.

National Steel, Stinson noted, filed a dumping complaint in the fall of 1977, then withdrew it at the request of the government. It could be refiled anytime, he added.