President Reagan has decided to ask Congress to overhaul the nation's antitrust laws to ease restrictions on mergers, and will argue that American businesses need greater flexibility to respond to global competition, administration sources said yesterday.

According to a memorandum by Treasury Secretary James A. Baker III, chairman of the president's Economic Policy Council, the president has approved a five-point legislative program recommended by his chief economic advisers to change the antitrust laws, which govern major areas of corporate activity.

The package, to be unveiled as part of the president's 1986 legislative agenda, will include a proposal to exempt import-battered industries from antitrust restrictions on mergers.

For other industries, another proposal would limit the grounds on which courts can block mergers.

Other proposed changes would severely restrict the use of treble-damage awards for violations of antitrust laws, would allow greater freedom to corporate directors to sit on the boards of competing companies and would sharply limit the ability of American firms to file antitrust suits against foreign corporations.

Sketchy information about the proposals emerged last month after the president's economic policy advisers presented him with their recommendations.

Details of the proposals approved by the president were made available for the first time yesterday by administration sources.

Federal antitrust laws, originally passed around the turn of the century, prohibit corporations from engaging in acts that may lessen competition through mergers, acquisitions or monopolization of a market.

The new proposals call for the first major overhaul of the antitrust laws in more than 35 years.

Some administration officials have argued that the antitrust restrictions on mergers may be discouraging transactions that would create stronger, more competitive firms.

Critics of the administration's antitrust policy have charged that weak enforcement of the antitrust laws has hurt U.S. competitiveness.

The president's package is likely to receive a mixed reception in Congress. House Judiciary Committee Chairman Peter Rodino (D-N.J.), said yesterday that he does "not foresee the Judiciary Committee countenancing substantial change or precipitous change in the antitrust laws."

Rodino, a frequent critic of the administration's antitrust policy, said, "if there is any connection between the antitrust laws and current economic policy, it would be that more vigorous competition -- not less enforcement -- is needed."

On the other hand, Senate Judiciary Committee Chairman Strom Thurmond (R-S.C.) is likely to give "very careful consideration" to the administration's proposals, said his spokesman, Mark Goodin.

Thurmond "would like to see sensible antitrust reform," Goodin said.

Some business groups have called for a more modest revision of the nation's antitrust laws, fearing that attempts to make broader changes will trigger too much opposition.

Administration officials involved in the preparation of the president's proposals seem more optimistic.

"It is quite reasonable to think Congress will react favorably to legislation that is solidly based," said Douglas H. Ginsburg, the Justice Department's antitrust chief, in a recent interview.

He said late last year that the legislative package being prepared was "considered, well-crafted, long overdue [and] extremely important to the competitive position of this country."

The package includes five specific proposals, according to an internal administration memo:

*The White House plans to propose a five-year exemption from the antitrust laws for mergers and acquisitions in industries that have been seriously injured by imports.

This provision would give the president an additional way to help depressed industries.

Under existing laws, if the International Trade Commission finds that an industry has suffered serious injury from foreign imports, the president can either do nothing or can offer protection by restricting imports with tariffs or quotas.

For example, Reagan drew criticism last fall for refusing to protect the declining shoe industry with tariffs and quotas, as the ITC recommended.

And administration officials complained loudly two years ago when two steel companies dropped their merger plans after the Justice Department raised antitrust objections.

A similar proposal is being pushed in trade bills by Sens. John C. Danforth (R-Mo.), John Heinz (R-Pa.) and Daniel Patrick Moynihan (D-N.Y.).

*In a change that could affect all industries, the president is seeking amendments to the 1914 Clayton Act that would make it harder for courts to block mergers.

The administration has argued that the Clayton Act, one of the historic pillars of antitrust law, is outdated because it was written at a time when economic understanding was less sophisticated and "social concerns" dominated antitrust philosophy.

Under current law, a court could block a merger if it would reduce jobs in the community or hurt a competing firm.

Under the president's proposals, the courts would have to find "a significant probability" that such transactions would enable the companies to engage in anticompetitive behavior, such as raising prices higher than competitive levels.

The courts also would have to evaluate proposed mergers and acquisitions according to the economic standards outlined in the Justice Department's merger guidelines, for example by looking at global rather than only local markets and considering the possibility of foreign competition.

*Another proposal would limit antitrust penalties to reduce the incentive of private companies to harass their competitors.

Now, when a company wins an antitrust case against another company, it can often collect treble damages.

Under the proposed changes, treble damages could be recovered only under a very few specified conditions. This provision also would allow the government to recover treble damages.

*One amendment would change the rules that limit corporate directors from serving on the boards of competing companies.

The existing law prohibits such "interlocking directorships" for companies that have capital, surplus and undivided profits of $1 million or more.

The administration wants to raise that threshold to $10 million and require that each company involved exceed that threshold before the law would apply.

*The president also has decided to propose restricting the ability of U.S. companies to sue foreign companies for alleged antitrust violations committed on foreign soil.

U.S. courts would be required to dismiss such suits unless a significant argument can be made that the court has jurisdiction or that U.S. consumers would be harmed.

For example, if a U.S. firm sues three foreign firms for allegedly anticompetitive activity overseas, an American court would dismiss the suit if the activity had a minimal or unintended effect on U.S. consumers, according to an internal administration memo.