Prime Minister Edward Seaga said today that American officials were involved with talks with Caribbean nations last week prior to the request for U.S. military assistance in invading Grenada.

"There was a representative from the State Department with ambassador title in Barbados Friday," Seaga said in an interview. "The Americans had been involved in the talks before Friday."

Seaga said the U.S. ambassadors to some of the Caribbean nations also took part in meetings to discuss possible responses to the assassination of former Grenadan prime minister Maurice Bishop and the takeover of the country by a "Cuban-style group."

The Jamaican prime minister said he could not remember the name of the State Department representative who was in Barbados the day before the Caribbean leaders convened in Trinidad and made a formal request for U.S. troops to lead the invasion.

However, Seaga said the United States did not prompt the Caribbean nations to request the invasion. He said the U.S. representative only "added to the concern over the turn of events in Grenada and the expanding Cuban and Soviet influence on the island."

Seaga said he was not aware of any U.S. request for participation in the rescue of former prime minister Maurice Bishop, as was alleged tonight by Prime Minister Tom Adams of Barbados. But he said he had heard reports of a request from the governor general, Sir Paul Scoon, for intervention by members of the Organization of Eastern Caribbean States.

He said the request activated the mutual protection provision of their regional defense agreement and it was only then that the organization sought military assistance from the United States and Jamaica.

Jamaica, with 150 soldiers in Grenada, is providing the largest Caribbean force in the conflict. The other five Caribbean nations involved together have 150 men committed. Jamaica is not a member of the Organization of Eastern Caribbean States but was asked to participate, like the United States.

"I have contended from the very beginning," said Seaga, "that Grenada has been following the usual communist course straight out, . . . promising changes, only to get close to Cuba and then shed their sheep's clothes and turn out to be wolves in the end.

"I watched it happen in Jamaica in the '70s," he said, adding that the newly built airstrip in Grenada and supplies of military equipment, as well as a Communist-run radio station, were leading to "the subversion and sabotage of the Caribbean."

Seaga said that while Bishop, the assassinated Grenadan leader, was a socialist and had contacts with Cuba, he was not seen as a threat to the other Caribbean countries.

"He was a moderate by comparison with these fellows," he said. "And he enjoyed good relations with the Caribbean community. . . . Fear of him commanding a successful takeover of other Caribbean islands did not exist."

Seaga, the United States' closest friend in the Caribbean since succeeding Michael Manley in 1980, said opposition by Manley and others to Jamaica's role in the invasion on the ground that it is a precedent for intervention in other countries was "imbecilic."

"Nobody wanted to invade a country," he said. "The OECS nations are under treaty obligations to assist one another. . . .I don't know why everyone is downgrading that treaty just because it is among small countries. It has legal, constitutional obligations and a member country used it to call for assistance."

Seaga acknowledged increased U.S. interest in Grenada in recent months but said Caribbean countries had independently become alarmed for their security. He said that no one could properly accuse Jamaica or the other Caribbean islands of acting as "puppets for the U.S."

The prime minister, who has aggressively courted the Reagan administration for economic assistance and who has been cited by Washington as a model for capitalism in the region, said he felt it was proper for the United States to share its worry about developments in Grenada and even to suggest a rescue for Grenadan officials before any formal request came from the Organization of Eastern Caribbean States.