A report yesterday incorrectly said Guatemala was one of four nations that have agreed to a proposed peace treaty in Central America. Guatemala has not agreed to the pact.

Prodded by the United States, four of five Central American nations have agreed on a draft regional peace treaty that would include roving international inspection teams to guarantee compliance.

The fifth country, Nicaragua, accepted an earlier draft of the so-called Contadora plan that does not include the inspection teams, and it did not attend the Oct. 19 meeting in Honduras where terms of this pact were drawn up. A copy was obtained by The Washington Post.

The newest draft, written by officials from El Salvador, Costa Rica, Guatemala and Honduras, reflects Reagan administration concerns raised in September when it appeared that all five nations, including Nicaragua, might sign the earlier version of the pact.

The administration had given a blanket endorsement to the peace process, launched 19 months ago by Mexico, Panama, Venezuela and Colombia on Contadora Island off Panama. But it had never expected Nicaragua to sign a regional treaty.

When Nicaragua announced its unconditional acceptance, the State Department was caught off guard and scrambled to check any potential Nicaraguan gains and put the U.S. seal of approval on a regional peace agreement. The department raised questions about security guarantees and scheduling of troop withdrawals.

Honduras obligingly summoned all nations of the region to discuss modifications. Nicaragua refused the invitation, charging that the meeting was taking place outside the Contadora framework.

"Nicaragua accepted the treaty . . . , and that remains our position," a Nicaraguan Embassy spokesman said yesterday. "We prefer that treaty. This one is also a proposal of the United States."

Embassy political counselor Francisco Campbell said, however, that the Nicaraguan Foreign Ministry "is looking at" the new version. Copies have been transmitted to all nations concerned, but no meetings about it are scheduled.

The new proposal revamps the structure governing treaty compliance so as to reduce the Contadora nations' role and turn to foreign ministers of the participating nations as final arbiters of disputes.

It eliminates a section that would ban all international military exercises in the area during arms talks -- a provision unacceptable to the United States -- and includes a new section to protect and help displaced persons within their own countries. A section that would halt arms acquisition during arms talks, and thus stop U.S. aid to El Salvador, was retained.

The new version withdraws and places "under study" a protocol in the previous draft by which nonsignatory nations such as the United States would have promised to do nothing to hinder treaty implementation. "The possibility of presenting an alternative instrument in the form of a 'Protocol of Guarantor States' has been considered," the draft said.

The draft would also establish within 60 days a detailed and binding schedule for a subsequent cease-fire, a military inventory, withdrawal of foreign troops and advisers and closure of foreign bases and schools.

A key U.S. goal was the concept of "synchronicity," or guaranteeing withdrawal of Cuban forces from Nicaragua at the same time U.S. forces leave Honduras and El Salvador.

Policing the initial stages would be a new "ad hoc disarmament group" whose duties would be "to stop the arms race in all its forms" and "to ensure compliance with the procedures" for disarming. The previous "Verification and Control Commission" would be retained, but Contadora nations would not be members.

There would also be an "international inspectorate" that would send inspectors to check military equipment and personnel levels, monitor the disarmament progress, verify arms purchases, establish a register of arms buys and investigate any reports of treaty violations.

The "units of inspectors," whose number is not specified, would be sent by four outside nations chosen by the Contadora group and approved by the Central American countries, on condition that they have not participated in the Contadora process.

The inspectors would be guaranteed "all facilities as well as prompt and full cooperation" of the nations signing the treaty. Their offices would receive security protection, and they would conduct their probes "through on-site inspection, compiling evidence and any other procedure they may deem necessary for the performance of their functions."

Their reports would go to the verification commission, which would give them to the nations concerned and recommend "solutions, sanctions or additional investigation" to them and to the foreign ministers. The commission's final reports would be made public.

If Nicaragua refuses to sign the new version, a Honduran official said, "We keep talking. Our interest is in having a treaty everyone can live with."