The Reagan administration scored a victory for itself in Central America last week when the Contadora peace talks bogged down. For weeks it had seemed that only minor modifications remained to be made on the draft regional peace treaty. But at a meeting of most of the interested parties last Friday, representatives of three countries - Honduras, El Salvador, and Costa Rica - suddenly said extensive changes were required before they could accept the plan.
The three countries' objections came after a short but intensive lobbying effort by the Reagan administration, say several United States and Central American diplomats and analysts. Nicaragua did not attend the meeting. And only Guatemala, which in recent years has pursued a foreign policy more independent of the US than most of its neighbors, stood in the way of the conferees adopting even further support for US position, some of these analysts allege.
Many US and Central American observers now expect the process of negotiation - once thought very close to completion - to drag on for months. Friday's meeting ended with a decision to name a commission that would study the issues raised.
The Reagan administration's overall view of the Contadora plan is that it consolidates the power of the Sandinista government. Republicans and Democratics in Washington say the administration specifically objects to the plan because it:
* Has the effect of withdrawing US advisers from El Salvador and Honduras before Cuban advisers must leave Nicaragua.
* Puts Nicaragua in the position of vetoing US arms shipments to El Salvador and Honduras.
* Confirms Sandinista hegemony in Nicaragua without any real democratization there.
* Contains inadequate provisions for the verification of Nicaragua disarmament and the cessation of Sandinista shipment of arms and munitions to the El Salvador guerrillas.
These objections are along the same lines as those raised by at last Friday's meeting.
US Democratic congressional observers assert that although some of these points may be ''legitimate,'' the Reagan administration's basic attitude has been one of not wanting to see any sort of Contadora treaty.
Both Democratic and Republican congressional observers told the Monitor that the hard-liners who seem to have the upper hand in administration policy do not believe it is possible to come to any real negotiated agreements with Nicaragua's Sandinista leaders.
Observers from both US political parties also said that one of the principal reasons the administration wound up mounting a massive, last-minute lobbying effort in Central America was that it had not paid much attention to the terms of the Contadora plan until the Sandinistas announced late last month they would accept the proposed treaty. Until that surprise development, the US did not expect anything would come of the Contadora process, the observers said.
Nicaragua's acceptance suddenly presented the Reagan administration with the prospect of a treaty with which it could not live.
The requests for changes have been unacceptable to the Sandinistas, who refused to attend Friday's meeting. And they are also unacceptable to Guatemala, which believes the US is trying to scuttle the draft treaty.
Daniel Ortega Saavedra, coordinator of the Nicaraguan junta, has sent a letter to area leaders suggesting a meeting be held by heads of state of the Contadora and Central American nations. Many analysts believe, however, that the US's regional allies will not accept that proposal. Until now, the Contadora negotiations have been conducted larged by the nations' foreign ministers.
Most US and Central American interviewed by this writer believe talks will drag on for months. But some of the most optimistic speak of a possible agreement by year's end. Meanwhile, talks between President Reagan's special envoy to Central America, Harry Shlaudeman, and Nicaragua's vice-minister for foreign affairs, Victor Hugo Tenoco, have slowed considerably.