Jaded cop. Impossible mission. Legions of gun-toting enemies.

Mr. Die Hard himself, Bruce Willis, has been down this block before.

So has director Richard Donner, whose 16 Blocks is a fairly benign, relatively tame echo of his Lethal Weapon flicks, presenting Willis in a passable variation of his familiar persona and co-star Mos Def in a strange but somehow likable sidekick role.

The story strains credibility at every turn as more and more New York City cops join to prevent aging detective Willis from delivering Mos Def to a grand jury, where he's the star witness in a police-corruption case.

And while the action is refreshingly restrained compared to the over-the-top cop thrillers that have aimed to outdo the Lethal Weapon series, none of the gunplay is interesting or clever enough to compensate for the dramatic shortcomings.

The result is tolerable but tepid, a movie with a steady, poky pulse that quickens slightly here and there during a few mild action highlights.

Willis's detective Jack Mosley is a man with a gimpy leg and a powerful thirst for hard liquor to fill the empty spaces between - and often during - tedious, go-fer shifts for the NYPD.

Jack's a cop who was once in the game, a top law enforcer and, we gradually learn, a man with a history of crossing some lines with former partner Frank Nugent (David Morse).

Now, Jack's a boozy burnout, so ashen and out of breath at times that 16 Blocks might be more aptly titled Diehard With a Defibrillator.

One morning, he's assigned a supposedly quick and easy task to run small-time crook Eddie Bunker (Mos Def) from a precinct lockup to a courthouse 16 blocks away where the grand jury is in session.

Eddie's got the goods on a gaggle of bad cops, and Frank and his associates intend to shut him up for good, even if it means going up against Jack.

Willis's performance is nicely stripped of Diehard-era wisecracks. Though Jack still is a generally superficial character, Willis manages to convey a sturdy sense of the man's inner turmoil behind his stoic facade.

Mos Def, who has shown an increasingly supple range in such movies as The Woodsman and The Hitchhiker's Guide to the Galaxy, here adopts a sort of Ratso Rizzo street-rodent patter that's tiresome and hard to decipher at times. Even so, the actor imbues Eddie with a charm and likability that somewhat offsets his slurry, blurry speech.

The screenplay by Richard Wenk imposes a silly and needless deadline from which many plot absurdities arise: The grand jury's session closes at 10 a.m., and if Eddie's not there by then, any information he has reaches its expiration date and becomes useless.

So in our judicial system, corrupt cops get a free ride if a grand jury can't get around to them in time? Why not just convene a second grand jury?

This contrived deadline apparently is in place to justify the movie's clock-is-ticking structure, the action playing out mostly in real time as Jack and Eddie claw their way through buildings, subways and crowded streets, Frank and his gang in pursuit.

But the sense of urgency is not integral enough to the story in a 24 sort of way. It ends up forcing Donner's hand, making him unnecessarily compact the story, whose action could have flowed along at the same pace without the pressure of things happening in real time.

Two stars out of four.