President Reagan today celebrated the 1983 U.S. military intervention here and said that aid to the anti-Sandinista rebels would enable the Nicaraguan people "to free themselves from communist tyranny and win the liberty you now enjoy in Grenada."

Bearing promises of more economic aid for Caribbean countries and a message of unrelenting anticommunism, Reagan told more than 20,000 cheering Grenadians in a cricket stadium on the edge of this steamy port city that the U.S. invasion halted "what appeared to be an attempt to turn your island into a staging area for subversion and aggression."

Reagan said that in Nicaragua "we see a chain of events similar to what happened here . . . . We hear the same excuses made for the communists, while the people of Nicaragua see their freedom, slowly but surely, eaten away." The president did not refer directly to the $100 million in military and economic aid he is going to ask Congress for the Nicaraguan counterrevolutionaries, also known as contras, but he said the United States "must help those struggling for freedom in Nicaragua."

Reagan was introduced by Prime Minister Herbert Blaize as "our own national hero, our own rescuer, after God."

To the beat of islands music and warm banners such as "Welcome President Reagan and Caribbean Heroes," Reagan, wearing a tropical suit and hatless, basked in an enthusiastic welcome.

But Nicaragua, not the U.S. military success on this English-speaking island, dominated the visit.

On Air Force One en route to Grenada, Elliot Abrams, the assistant secretary of State for inter-American affairs, told reporters that the Sandinistas will not negotiate with the opposition in Nicaragua unless forced to do so by arms. His comment was made when he was asked about the position of Oscar Arias Sanchez, the president-elect of Costa Rica, who has opposed military aid to the contras and called for negotiation instead.

"It's crystal clear to us that the way to get them to negotiate is to force them to negotiate," Abrams said. "There comes a point -- and we reached it in Grenada and we've reached it in Nicaragua -- where no amount of talking will change the situation."

Abrams said "a real turning point" had been reached in the Nicaraguan war and that the Sandinistas hope to delay a vote on U.S. military aid to the rebels until after the current dry season with the hope of wiping out the contras this year.

But Reagan said during a picture-taking session with Governor General Sir Paul Scoon that the success of military force in Grenada had not given him any thoughts of using U.S. military force in Nicaragua.

"No, I think that's an entirely different situation," Reagan said. When reporters pressed him on ruling out U.S. force, he added, "I never had plans for such a thing."

In his speech in Queen's Park, the president focused on the dangers of communism in the region.

"As we rejoice in your renewed freedom, let us not forget that there are still those who will do everything in their power to impose communist dictatorship on the rest of us," Reagan said. "[Cuban President Fidel] Castro's tyranny still weighs heavily on the peace and freedom of the hemisphere. Doing the bidding of his faraway masters, he has shipped Cuba's young men by the thousands to fight and die in faraway lands. When one recalls the tons of military equipment captured here, we can thank God things were changed before young Grenadians, too, were sent off to fight and die for an alien ideology."

Reagan was applauded by a noisy crowd that had been let off work or school for a national holiday in the president's honor. Many waved both U.S. and Grenadian flags.

The president spent nearly five hours on this island in a carefully orchestrated visit in which he met with leaders of nine English-speaking nations in the Caribbean and laid a wreath on a memorial at the St. George's School of Medicine to the 19 U.S. servicemen killed in the Oct. 25-Nov. 2, 1983, invasion.

One-hundred fifteen U.S. servicemen were injured in the operation, which has been criticized in retrospect for inefficiency by U.S. military planners. Twenty-five of the Cuban defenders of Grenada, most of them armed laborers, were killed and 59 wounded. The civilian toll on Grenada was 45 killed, including 21 at a mental hospital hit by U.S. bombs, and 358 wounded.

Reagan said that the U.S. intervention was in response to an "urgent request" for aid from six members of the Organization of Eastern Caribbean States, joined by Jamaica and Barbados. He said the operation had rescued 800 U.S. students at the medical school "whose lives were in danger."

Reagan brought with him a few governmental gifts designed to show that he understands the economic plight of the hard-pressed Caribbean nations, where unemployment is up and exports to the United States are down.

One was a program designed to provide increased access to the U.S. clothing market by increasing quotas for apparel assembled in Caribbean nations from cloth woven and cut in the United States. But the administration is so politically sensitive to the depressed domestic textile industry that no figures for the increased quota were announced and U.S. officials told reporters that any increase in Caribbean imports would be subtracted from the totals of countries in other regions.

The other initiatives included $5.5 million in direct aid from the Agency for International Development to assist English-speaking Caribbean nations in improving their legal systems and a program raising U.S.-funded scholarships for Caribbean students from 500 in 1985 to 1,500 in 1988.

Reagan discussed the Caribbean Basin Initiative (CBI) in glowing terms in a speech Wednesday but was more restrained on Grenadian soil, saying "whether the CBI succeeds and the economies of the Caribbean prosper depends as much on what you do as on what we do."

In any case, he said, the result will be preferable to what has happened in Cuba, where "Castro has turned a once-thriving economy into a basket case."

While the overwhelming majority of Grenadians were enthusiastically friendly to the president, about two dozen supporters of murdered Marxist Prime Minister Maurice Bishop gathered in the town square to protest the visit. About 15 persons were arrested Wednesday night by a U.S.-trained Grenadian paramilitary unit when they became rowdy during a rehearsal of the presidential motorcade at the town harbor.

The president's plane landed at the Point Salines Airport, under construction by Cubans when waves of Air Force C130s dropped paratroopers onto the runway early the morning of Oct. 25, 1983. Reagan had cited the airport and its 10,000-foot runway as evidence that the Cubans were preparing the island for military equipment.

Reagan was reportedly troubled by the turbulent flight but was in high spirits as he received a hero's welcome.

The president expressed gratitude for the reception in a conversation with reporters after he met with the Caribbean leaders. But when he was asked how it felt to return to the site of his "greatest military triumph," Reagan replied with a smile, "I didn't fire a shot."