Murder and intrigue stir up Nicole Kidman's hot African blood in Sydney Pollack's “The Interpreter,” a bulky, deliberate thriller that delivers a generous portion of suspense, but — as far as its leading lady is concerned — never completely suspends our disbelief.

Which isn't to say that Kidman (“The Stepford Wives”) isn't completely fetching as United Nations interpreter Silvia Broome, a willowy, blonde stunner who speaks a half-dozen languages, plays the flute and looks smashing in black. Translating tense, closed-door meetings between the grumpy American delegation and members of various delinquent Third World entities, Silvia is a state-of-the-art U.N. functionary; with her sexy, Afrikaans-lite accent, she could even make “We're going to bomb you” sound solicitous.

Returning to the U.N.'s New York offices late one night to retrieve some personal belongings, Silvia dons her headset and overhears whispered details of an assassination plot, picked up by a microphone on the darkened assembly floor. Escaping into the night, Silvia surmises that the target is one Dr. Zuwanie (Earl Cameron), iron-fisted ruler of the fictional African nation of Matobo, due to arrive in New York to answer charges of genocide.

Silvia alerts the proper authorities, who in turn put Secret Service agent Tobin Keller on the case. Played with a burning undercurrent of grief by Sean Penn (“Mystic River”), Keller is a still-bereaved widower who's spent most of his career escorting foreign dignitaries to strip clubs (“Don't touch the prime minister,” his partner, played by Catherine Keener of “Being John Malkovich,” warns a dancer). Nonetheless, Keller is an ace gumshoe and thinks that Silvia is lying, for reasons unknown.

For all we know, Silvia is a liar, since the overheard conversation was conducted in Ku, a Central African dialect invented for the movie. Soon, details emerge about Silvia's past that cast further suspicion on her motives — for instance, the fact that Silvia grew up in Matobo, and that her dear parents were killed by a land mine planted by Zuwanie's men. If Zuwanie's appearance before the U.N. is somehow thwarted, it will improve the chances of the dictator being tried before the World Court in The Hague.

Pollack, whose 1975 political thriller “Three Days of the Condor” remains one of the classics of the genre, keeps us on our toes. The question of Silvia's motives keeps the suspense flowing, churned up by the intriguing menagerie of assassins, political pariahs and shady acquaintances who cross her path. Pollack has a tendency to err toward the ponderous — most blatantly in the dirgelike Harrison Ford romantic drama “Random Hearts” (1999) — and he indulges a bit of it here, particularly with scrolling, reverential shots of the New York skyline.

Diplomatically speaking, Kidman is as good as she could be in the role. When Silvia, hoping to allay Keller's suspicions of foul play, describes a Matoban rite of forgiveness and how it informs her personal philosophy, character and actress fuse into one.

However, the performance loses its bite when Pollack and his trio of screenwriters (including Scott Frank of “Get Shorty” and Steven Zaillian of “Traffic”) unwisely hitch the finale to Sylvia's feelings of betrayal and genocidal agony. No matter how impassioned Kidman's performance, she is simply not a compelling or credible mouthpiece for African misery, especially so soon after the fact-based horrors of “Hotel Rwanda.”

Consequently, “The Interpreter” hits an emotional wall, and Silvia — for all her linguistic expertise — stops speaking our language.