In a pivotal scene in ''Hotel Rwanda,'' which opens Wednesday, the colonel in charge of a beleaguered United Nations peace-keeping force rushes to talk with the commanding officer of a fresh and heavily armed United Nations contingent that has just arrived at a hotel packed with refugees from the bloody genocide outside its walls. The colonel, played by Nick Nolte, suddenly throws his blue beret on the ground in anger. The eyes of the hotel manager, played by Don Cheadle, slowly register concern, then fear. The awful truth becomes clear: the new soldiers are there to evacuate the mostly white foreigners, leaving the black Rwandans to their fate.

''That gets to you -- they were counting on the U.N. and they were abandoned,'' whispered Anthony Lake, as he watched the scene in an otherwise empty theater here. Mr. Lake, the national security adviser in the Clinton administration, played a role in determining United States policy in Rwanda a decade ago, and he had agreed to attend the screening of a movie that, even before its release, is provoking uncomfortable memories of the collective failure by Western powers to confront an atrocity.

''Hotel Rwanda,'' from MGM's United Artists unit, depicts the events of 1994, when Hutu extremists slaughtered some 800,000 of their countrymen, women and children. The genocide of the Tutsis and moderate Hutus was probably the fastest and most personally brutal in history: more often than not, the implements for death were machetes.

To deal with its burden of horror, the film searches out a bright spot. Like ''Schindler's List,'' it concentrates on a real-life hero, Paul Rusesabagina, the fastidious, crafty and courageous manager of a luxury hotel in Kigali, the capital city. For two and a half months, Mr. Rusesabagina, a Hutu, held insanity at bay. Somehow, using his connections to the Hutu army command, bribes of money and single malt Scotch, flattery and threats, and desperate telephone calls to the outside world, he was able to save the lives of 1,268 people who took refuge in his hotel, the Milles Collines, including his Tutsi wife and their four children.

The director, Terry George, has taken pains to make the movie watchable and to retain its PG-13 rating. There are plenty of bodies -- including a grisly scene reminiscent of the bone yard in ''The Killing Fields'' -- but the massacres occur in peripheral vision. They are depicted mostly in a fictionalized piece of videotape. (Mr. George was persuaded not to use actual videotape of people being killed.)

People familiar with what happened 10 years ago in Rwanda, both those inside and outside the country, are coming face to face with scenes that remind them of their own trauma and shame, much of it grounded in the fact that the world willingly turned its back on what was happening there.

Mr. Lake, for his part, requested two ground rules in agreeing to see and discuss the film: that he not be made to appear ''self-serving or self-exculpatory'' (a rule that tended to take care of itself), and that he be allowed to air his views on the current situations in Darfur in Sudan and in the eastern Congo. The extensive loss of civilian life in those places, he believes, is a direct echo of the Rwandan genocide, and this time, he asserts, international powers should not sit idly by, as they have largely done to date.

In Rwanda, the United States did not simply not intervene. It also used its considerable power to discourage other Western powers from intervening. At the height of the carnage, when Belgium lost 10 peacekeepers, the United States demanded a total United Nations withdrawal. Some African countries objected, and eventually Washington settled for a severe cutback in the 2,500-man United Nations force. The commander of the force in Kigali, Maj. Gen. Rom?Dallaire of Canada, who had asked for 5,000 troops, was left with 270.

The withdrawal, Paul Rusesabagina noted, was a critical turning point. In an interview in New York, where he was promoting the film, he said it signaled to the Hutu militia, known as the Interahamwe, that their planned killing of Tutsis and moderate Hutus could continue unabated.

''You can imagine the situation,'' he said, describing a scene of dead bodies piling up in the streets outside his hotel. ''The majority of the population is now killing systematically the minority, and no one just raises a finger to say this is wrong. And even the United Nations is pulling out.

''Everyone was listening to radios so we all knew what was going on in the Security Council. When other countries wanted to maintain their soldiers the U.S. said no. Of course I was angry against each and everybody. I was bitter. It's because it was Rwanda. It was Africa. What else can you conclude?''

With time, his anger has dulled, he said: ''By now I have come to realize that the average person outside is not always aware of what was going on. But the leaders were aware of what was happening.''

Mr. Lake, now a professor of international diplomacy at Georgetown University, said he had reviewed memos of the time in an attempt to reconstruct the government's position. The goal was not to ''wallow in guilt,'' he said, but to understand why the slaughter in Rwanda registered so faintly in the Washington decision-making apparatus.