PAN AMERICAN GAMES : Fervor Smooths the Rough Spots : Opening: Cubans’ warmth after five years of struggle to complete the games’ facilities helps offset the poor workmanship on display at some venues.

With nature contributing thunder and lightning as special effects, and with the Caribbean Sea as a backdrop, one of the few men in the world who could have commanded attention in such a setting, Cuban President Fidel Castro, officially opened the Pan American Games on Friday at the Olympic Stadium.

Wearing his customary green army fatigues, Castro, while ominous thunderclouds spread across the horizon, silenced a jubilant crowd of about 35,000 at the opening ceremony with a formal, 10-word sentence in Spanish that Cubans have anticipated since the cities of Havana and Santiago de Cuba were awarded the Games.

It has been an exhausting, expensive five years, filled with questions reaching all the way to Castro’s office at the Palace of the Revolution about whether the estimated $156-million effort should be continued during an economic crisis and doubts in the rest of the Americas about whether it would be successful.

That remains to be seen. More than 5,000 athletes from 39 North, South and Central American and Caribbean countries begin 16 days of competition in 31 official sports today with a 6:30 a.m. (EDT) start for the men’s marathon.

But Dr. Evie Dennis, the leader of the 851-member U.S. delegation, needed only one word to sum up the results so far.

“Magnificent,” she said.

By U.S. standards, that is an exaggeration. Some of the 21 new sports facilities already are showing wear because of inferior construction materials. And the field in one of the old stadiums, the Antonio Maceo Sports Center in Santiago de Cuba, was almost deemed unplayable by soccer’s international federation. After an inspection Friday, it approved the field for first-round games.

But considering that Cuba is a Third World country, isolated not only geographically but politically and economically as many of its former allies turn away from communism, most U.S. athletes and officials have been impressed with the achievement. They are less impressed by the living standards of those who achieved it by working around the clock in recent weeks.

Castro promised earlier this year that Cuba would win a gold medal for hospitality, and the 200 or so U.S. athletes--of 685 entered in the Games--who marched in the opening ceremony in powder blue shirts and khaki pants were greeted politely by the crowd, despite the tension between the U.S. and Cuban governments that is advertised on billboards throughout Havana.

The absence of diplomatic relations between the two countries was an obstacle for COPAN, the local organizing committee. U.S. government restrictions on trade with Cuba almost scuttled the bowling competition because there were no lanes or automatic-pin setters in the country. Drug-testing was imperiled by the difficulty in acquiring sophisticated laboratory equipment, as was television coverage to the United States because of the $9 million in rights fees that the organizers expected to receive and didn’t.

But those problems were solved when Japan provided the bowling equipment, Mexico provided a portable drug laboratory, and Castro, in what he called a gift to American sports fans, allowed two networks, ABC and TNT, to have the television rights for free. The U.S. government did its part by relaxing its rules governing travel to Cuba, allowing members of athletes’ families to visit here during the Games.

Including tourists, athletes, officials and media, more U.S. citizens, almost 1,800, are in Cuba for the Pan American Games than at any time since the revolution in 1959.

Jim Schreiner, a 26-year-old kayaker from Day, N.Y., who has continued to compete at a high level despite suffering from multiple sclerosis, carried the U.S. flag in Friday’s opening ceremony, declining, as has become tradition with U.S. teams, to bow it to a foreign head of state.

Castro sat in a heavily guarded dignitaries’ box with presidents of the International Olympic Committee, Juan Antonio Samaranch of Spain; the Pan American Sports Organization, Mario Vasquez Rana of Mexico; and the local organizing committee, Jose Ramon Fernandez Alvarez.

Fernandez, who also serves as a vice president for Cuba’s Council of Ministers, was the commander of the battalion that turned away the U.S.-supported counter-revolutionaries during the Bay of Pigs invasion almost three decades ago. But Friday’s three-hour ceremony was devoid of political overtones, focusing on musicians, dancers, gymnasts, parachutists and, of course, the athletes.

Volleyball player Joel Despaigne carried the torch on the final leg of a 1,400-mile run into the Olympic Stadium, where he handed it to high jumper Javier Sotomayor, who was elevated to the caldron on a small escalator that made it appear he was floating. He ignited the flame at the same time as a lightning bolt flashed across the sky.

In a country where mysterious Caribbean religions flourish, it could have been some sort of omen. But it definitely was a portent of rain, which sent spectators scurrying for cover even as another world-class Cuban athlete, quarter-miler Ana Fidelia Quirot, recited the athlete’s oath.

On an afternoon that began under a clear, blue sky, the crowd was never more exuberant than when the 609-member Cuban team appeared in the stadium during the parade of nations.

Greeted by hundreds of Cuban flags, and hearing the cheers and the loud, rhythmic music, the athletes did not so much march as rumba around the track.