Two key House committee chairmen yesterday urged President Carter to delay the signing of the new agreement governing air service between the United States and United Kingdom for 30 days to give Congress a chance to review the pact.

Their request came amid growing reports that the agreement may be more restrictive and anticompetitive than U.S. officials have suggested, and in fact may belie the policy direction the President has enunciated.

Noting that "numerous objections to the agreement have been received, Reps. Harold T. (Bizz) Johnson (D-Calif.), chairman of the House Public Works and Transportation Committee, and Glenn M. Anderson (D-Calif.), chairman of the Aviation Subcommittee, said a 30-day postponement would allow the Congress to explore the matter in detail and "in an unemotional manner" without causing injury to U.S. or U.K. interests.

The agreement, hammered out in London minutes before a midnight deadline June 21, is scheduled for signing in a formal ceremony on Saturday in Bermuda.

The agreement would replace one in effect since 1946 but denounced a year ago by the British who hoped to negotiate a new one giving their air carriers a greater proportion of the air travelers between the two countries.

Only cursory details were available to officials in Washington after the agreement was initialed, but the clear impression given by them - perhaps to them, some sources say - was that the U.S. had held firm on its basic principles, but had sought to meet the "legitimate concerns" of the British about excessive capacity being offered on the North Atlantic by the airlines at times.

Details of the agreement still have not been publicly disclosed but sources who have seen it say the U.S. may have given up much more than originally believed. "It's atrocious," said one source, complaining that it represents "a total abdication" of longstanding principles ascribed to by the U.S.

For instance, he said the agreement outlines specific capacity restrictions never before contained in bilateral air agreements. For a number of routes, the agreement specifically states that there may be no more than a certain number of flights per week. In the past, schedules were left up to the airlines.

Sources say also that competition is almost permanently limited to the status quo, eliminating the possibility that a new U.S. carrier, like Britain's Laker Airways, could propose and institute new low-fare service between the U.S. and the U.K. Because there cannot be more than one U.S. carrier per market (except in Los Angeles and New York), a new competitor would first have to find some city pair no one else serves and then induce the British to accept it. Both are said to be unlikely.

"We ended up with an agreement that's all give and no take," one offficial said. "I just don't understand why we proceeded that way; we had no reason to be frantic to get a new agreement. The British are far more dependent on air services than we are, and they benefit greatly by the travel between the two countries. We supply more passengers."

Besides the Johnson-Anderson letter, sources said numerous other legislators have complained to the President that the still secret agreement may not be all he wants.

Letters were apparently sent by Sens. Howard W. Cannon (D-Nev.), Edward M. Kennedy (D-Mass.), Alan Cranston (D-Calif.), S.I. Hayakawa (R-Calif.), and Paul S. Sarbanes (D-Md.) (Baltimore is forclosed by the agreement from getting scheduled service to London unless a carrier from Washington drops out because Baltimore is grouped with Washington as one city for purposes of the agreement.)

Cannon is said to have told the President that the agreement, in restricting competition, runs counter to his publicity stated policy of encouraging competition in foreign air travel.

Asking his personal intervention in the matter, Cannon and others have complained that the agreement is already being used as a precedent. The Japanese have begun negotiations for a pact patterned after the British.