For want of congressional renewal, legislation expires today that enabled major American oil companies to cooperate with the International Energy Agency in planning how the United States would share petroleum with 20 other countries in the event of a new oil crisis.

Although the limited antitrust exemption given American companies to let them participate in the IEA is being allowed to lapse for the first time since 1975, the change is not expected to have any immediate impact on the work of the organization, because no IEA meetings are scheduled in July or August.

"It is unfortunate that this happened from the standpoint of continuity of U.S. energy policy, but it does not signify any lessening of our commitment to the IEA, and Congress undoubtedly will renew the exemption pretty quickly after it returns from the July 4 recess," a House source said.

The 21-nation IEA was established in the aftermath of the Arab oil embargo that followed the 1973 Middle East war. Every month the major American oil companies, along with 27 foreign petroleum companies, provided the IEA with confidential reports covering imports, exports, inventories and production levels. On the basis of this information, the IEA Secretariat established allocation figures for each of the participating countries in the event of an emergency.

Both the Senate and the House have approved bills extending the antitrust immunity of the American oil companies, but the legislation is bogged down in a dispute over Senate amendments that would force changes in the Reagan administration's policies relating to the nation's Strategic Petroleum Reserve.

The Senate bill, passed 88 to 7 on May 26, would require that the administration increase the rate at which it is filling the emergency reserves--stored in salt caverns in Louisiana and Texas--to an average of 300,000 barrels per day. It also would require that the White House submit to Congress a plan that would spell out when it would use the reserves.

"The administration views the Senate plan as unacceptable," Assistant Energy Secretary Robert C. Odle Jr. said yesterday.

The House bill, passed 396 to 3 on June 23 and much more to the administration's liking, sets the fill rate for the strategic reserve at 200,000 barrels per day and does not require administration submission of a draw-down plan.

The White House has argued that increasing the reserves more rapidly would be far too costly, as it would require construction of temporary storage facilities. It also opposed making public its plans for using the emergency reserves, on the grounds that this would remove one of the main incentives private oil companies have for maintaining adequate supplies.