Nicaraguan junta leader Daniel Ortega charged in a U.N. speech today that direct U.S military action against Nicaragua, modeled on last year's invasion of Grenada, will be "ready to begin" Oct. 15.

He later cited "intelligence information from various sources" and increased U.S. military activity near Nicaragua's borders as evidence to back up his claim.

State Department officials here dismissed the charge as "nonsense." A Pentagon spokesman said the charge was "utter nonsense," adding that there is at present only one U.S. ship off the coast of Central America and that Green Berets are participating in relatively small-scale exercises in Honduras.

Addressing the U.N. General Assembly, Ortega said Defense Department and CIA plans included renewed mining of Nicaraguan ports, air and sea attacks and the taking of territory, all justified by a false call for aid from other Central American nations.

"They have the actors in their assigned places with their roles memorized," he said.

The speech was the high point so far of a week-long U.S. visit designed to be a media and speech-making blitz by Ortega and other members of Nicaragua's leftist Sandinista government. It is timed to coincide with key votes in Congress on the future of U.S. aid to rebels known as contras trying to overthrow the Sandinista government.

Ortega said Nicaragua is suffering from "the genocide of the U.S. authorities' terrorist policies." He called on the United Nations to insist that the United States approve a draft peace treaty for Central America proposed by the Contadora group made up of Colombia, Mexico, Panama and Venezuela.

In his speech, the text of which was made available, Ortega said other Central American governments were prepared to "go through the formality of requesting 'aid' from the United States to eradicate the 'Sandinista threat' from the area." The Pentagon has positioned U.S. forces "for bombings, troop landings and direct incursions into Nicaragua," has drafted an estimate of U.S. casualties and is prepared to name "the puppet who would serve as the future president backed by the United States in Nicaragua," Ortega said.

He said "intelligence information from various sources" had discovered "intense activity in the U.S. Southern Command" headquarters in Panama, including meetings with mercenaries, a concentration of anti-Sandinista forces in northern Costa Rica, an increase in U.S. naval forces off the Nicaraguan coasts, and more reconnaissance and helicopter flights over Nicaraguan territory.