President Daniel Ortega today threatened military action to free eight West Germans kidnaped in May if their captors, U.S.-backed rebels, have not released them by Monday at 6 p.m. (8 p.m. EDT).

Charging that the United States, as supporter of the anti-Sandinista guerrillas, known as counterrevolutionaries or contras, is responsible for the release of the West Germans, Ortega said, "We hope that in the next hours or tomorrow they will be freed. If not, the only alternative remaining will be a military recourse."

Ortega told a press conference after meeting with Bonn's special envoy Hans-Juergen Wischnewski, that if a military operation is necessary, measures will be taken to minimize risks to the hostages as much as possible.

The Nicaraguan leader's statement came despite a strongly worded request from West German Chancellor Helmut Kohl not to use force. In a letter to Ortega, the German leader said, "It seems important to me that the government of Nicaragua continues maintaining the cease-fire" that was declared in the area. He warned that "the evolution of this serious issue will be reflected in the relations between our two countries."

The German volunteer workers, four men and four women, were kidnaped in the village of Jacinto Baca during a raid by the U.S.-backed Nicaraguan Democratic Force. They reportedly have been held in the jungle region of south-central Nicaragua.

In Tegucigalpa, Honduras, Frank Arana, a spokesman for the U.S.-supported Nicaraguan Democratic Force, said, "We are at war with the Sandinista regime and we will confront militarily any situation that occurs." He predicted the Germans would be released to International Red Cross officials sometime this week, The Associated Press reported.

Ortega charged that the contras broke an agreement to release the German hostages last Thursday. He said the contras are now proposing new conditions that are "totally absurd," adding that Nicaragua cannot agree to them. He would not give details on what the conditions were.

One diplomatic source said that the contras were requesting a liberated zone. Another diplomatic source said that the contras were insisting that they be present at the exchange. The sources said it was not clear whether the Sandinistas were serious about the threat to take military action or whether they were bluffing to force a release.

"They could be trying to push the contras into a deal they don't want," a diplomat said.