BASIC

Exasperating military thriller.

Running time: 98 minutes. Rated R (violence and language). At the Empire, the Lincoln Square, the Kips Bay, others.

IN the clumsy military suspense thriller “Basic,” expositional tracts are as incessant as the rain that pummels the Panamanian setting.

But they don’t help much.

A soldier’s version of Clue – was it the Ranger with the grenade in the jungle, or the drug-runner with the machine gun in the shack? – “Basic” chases its tail for so long, it morphs from a whodunit into a who-cares.

An unusually buff John Travolta, slipping back into the military mode of “Broken Arrow” and “The General’s Daughter,” commands the screen with innate star power and a touch of that old Vinnie Barbarino swagger.

And action director John McTiernan – who has gone from the high of “Die Hard” to the low of last year’s “Rollerball” – does an adequate job filming the waterlogged jungle maneuvers.

But screenwriter (and co-producer) James Vanderbilt’s knottier-than-a-pretzel script, with its seemingly endless maze of lies and deceptions and flashbacks and triple-crosses, will make your head ache.

Travolta plays ex-Army Ranger turned D.E.A. agent Tom Hardy, a wild card with ace interrogating skills and “a colorful past” (denoted by the fact that he is swigging Jack Daniel’s from the bottle when we first meet him).

An old buddy, U.S. Army base commander Col. Bill Styles (Tim Daly), calls Hardy in after a routine training exercise in the jungles of Panama has, according to one apt description, gone “pear-shaped.”

Six Special Forces trainees went out during a hurricane under the command of the sadistic Sgt. Nathan West (Travolta’s “Pulp Fiction” co-star, Samuel L. Jackson), but only two returned – and they’re not talking to the military police captain assigned to investigate.

After some sexually charged to-ing and fro-ing between Hardy and off-the-case Lt. Julia Osborne (“Gladiator’s” Connie Nielsen, with a Southern accent that dips and wanes), Hardy gets them to spill.

It appears their comrades were murdered, but this is where the script unconvincingly veers into “Rashomon” territory, as the two survivors – Dunbar (Brian Van Holt) and Kendall (Giovanni Ribisi), the gay son of a high-profile Joint Chiefs of Staff official – return to the scene of the crime in a convoluted series of flashbacks.

As Dunbar and Kendall continually revise their stories under pressure from Hardy and Osborne – who have now forged an uneasy truce – the plot turns into impenetrable pea soup with the addition of a drug-peddling medic (Harry Connick Jr.) and even more finger-pointing.

Yet the person behind the cover-up is obvious pretty early on.

Even though the concluding “twist” is a neat one, you’ll have expended so much energy sorting out this glossy but ultimately indecipherable Rubik’s Cube, you’ll be too worn out to care.