The Carter administration yesterday pledged to abide fully with the 1973 War Powers Act limiting presidential war-making authority but opposed proposals to tighten its provisions.

The controversial and historic law was passed by Congress in reaction to the Vietnam war over the strong opposition of President Nixon and a veto by President Ford.

President Carter, in response to a question in his radio "call-in" show four months ago, called the law "an appropriate reduction" in the authority which Presidents have had in the past. Carter said would not knowingly approach a time of war without letting the public know what was going on.

State Department legal Herbert J. Hansell told the Senate Foreign Relations Committee yesterday that "this administration as a matter of policy intends to follow the letter and spirit" of the key section which requires congressional approval within 60 days of U.S. military action overseas.

Hansell also said the administration is "firmly committed" to making meaningful and prompt reports to Congress on U.S. military deployments in potential combat zones as required by the law. President Ford submitted sketchy reports on four occasions without ever conceding that the law required him to do so.

In a display of congressional base-touching, high administration officials telephoned at least a dozen senior members of the Senate and House around midnight Wednesday shortly after receiving word that a U.S. cargo helicopter had been shot down over North Korea. Secretary of State Cyrus R. Vance and Secretary of Defense Harold Brown wielded the telephones from the White House Situation Room, where they were meeting with Carter and presidential advisers.

The law did not require a report on the helicopter incident unless a war resulted of U.S. combat forces were redeployed. However, the late night telephone calls may have contributed to the calm congressional reaction to the incident Thursday and they seemed to some lawmakers an indication of presidential concern to keep Congress informed.

Sen. Jacob K. Javits (R-N.Y.), one of the sponsors of the war powers act, called the pledges of compliance "extremely refreshing" and said that excutive branch acceptance means that "we are now faced with the problems of the trees and not the forest."

Speaking for the administration. Hansell opposed proposals to amend the law, saying that conscientious compliance should be given time to work and that a prolonged debate on changes could produce new uncertainties "in the minds of our allies and potential adversaries."

Sen. Thomas F. Eagleton (D-Mo.) and Rep. Stephen J. Solarz (D-N.Y.) proposed amendments to tighten the law in testimony before the Foreign Relations Committee earlier this week. Sen. Barry Goldwater (R-Ariz), on the otther hand, called on Congress to repudiate the "dangerous" and "unconstitutional" measure.