Washington — The Reagan administration is paying a potentially heavy price - not only in Congress but also among its European allies - for its apparent support for laying mines in Nicaraguan harbors.
Congressional concern has grown to the point that a combination of forces, both in the Senate and House, might cut off $21 million in proposed ''covert'' aid to the guerrillas fighting the leftist-led government of Nicaragua.
The European allies' concern appears to center on three considerations: (1) that the mining of Nicaraguan ports disrupts the universally recognized principle of the freedom of navigation; (2) that European seamen might be killed or injured in Nicaraguan ports; and (3) that Soviet or East European ships could be damaged, thus leading a regional conflict further in the direction of superpower conflict.
cc20p6 As an added consideration, the French Foreign Ministry has stated that the mining of Nicaragua's harbors had already prevented ships carrying ''humanitarian supplies,'' such as food and medicine, from unloading their cargoes in Nicaragua.
France has offered to help Nicaragua sweep the mines from its harbors, although there is no indication that any such French action is imminent. Britain last week informed the Reagan administration that it disapproved of the mining operations.
European diplomats said the protests derived in part from a conviction that the US Central Intelligence Agency was directly involved in supervising the operations, which, according to press reports, have been carried out by non-Nicaraguan, Latin American employees of the CIA.
British concern apparently increased toward the end of last month after a ship carrying British seamen under the Liberian flag struck a mine upon entering a Nicaraguan port. No one was injured in this case.
But the mines are reported to have damaged vessels from six nations over the past six weeks. Several Soviet seamen are reported to have been injured in one mine explosion.
In briefings for senators and congressmen planned for today, administration officials are expected to argue that the mining will cut the flow of military supplies passing from the Soviet Union and Cuba through Nicaragua to the guerrillas fighting the US-backed government of El Salvador.
The mining does indeed appear to be slowing down shipping to Nicaragua. It is also slowing down Nicaraguan exports. A recent visitor to Managua said that coffee is piling up on the Nicaraguan docks.
From the Reagan administration's point of view, this is fair play, because the Salvadorean guerrillas, who are accused of having strong Nicaraguan backing, have long made it a policy to attack economic targets, such as bridges, coffee mills, and electrical and transportation facilities.
The administration has argued in the past that covert aid to the anti-Sandinista guerrillas fighting in Nicaragua might force the Sandinistas to stop ''exporting revolution'' in Central America. Congressional critics contend that the aid violates international law and undermines efforts of the four Latin American nations, known as the Contadora group, which are trying to facilitate a regional peace settlement.
On Sunday, the four foreign ministers in the group - from Mexico, Venezuela, Colombia, and Panama - said the mining had contributed to a ''grave deterioration'' in Central America.
But what concerns some senators and congressmen more than anything else at the moment is the Reagan administration's decision last week to refuse to accept for the next two years the jurisdiction of the International Court of Justice for any cases arising from US actions in Central America.
On Monday, Nicaragua asked that court, which is often called the World Court, to order a stop to the US-sponsored mining of its ports and to attacks on its territory.
Nicaragua has charged that US-supported guerrillas, as part of a ''destabilization'' effort, have killed more than 1,300 of its citizens and caused more than $200 million in damage.
In defending its decision to decline giving the World Court jurisdiction over the Nicaraguan suit, the administration cited four precedents for nations saying they will not accept such jurisdiction. The nations concerned were Australia, India, Britain, and Canada. Some administration officials charged that Nicaragua merely intended to use the court for a propaganda display.
But House Speaker Thomas P. O'Neill Jr., a Massachusetts Democrat, concluded that administration policy was now not only ''immoral'' but also ''illegal.'' Mr. O'Neill told reporters on Tuesday the House of Representatives was not likely to grant any funds for the CIA-sponsored Nicaraguan rebels.