NEW YORK -- As an arena for serious plays probing timely issues, Broadway tends to be on a par with your average amusement park. Gut thrills are the order of the day, and the blockbuster hits have much in common with those daredevil rides that propel the customer through a series of heart-clutching loop-de-loops. One ("Starlight Express") even looks like a ride.

If only because it bucks the tide, "A Walk in the Woods," which opened last night at the Booth Theatre, deserves a handshake and a warm clap on the back. Lee Blessing's thoughtful and sober two-character drama dares tackle the forbidding subject of arms negotiations between the superpowers. More specifically, it looks at a starchy and priggish American (Sam Waterston) and a bluff and affable Russian (Robert Prosky) as they fight their way through the thickets of national policy and prejudice.

If, in the end, the work never delivers a big dramatic punch, it gives Prosky -- one of the most successful actors to emerge from Washington's Arena Stage -- a rich role, which he plays with shrewd joviality. His is not the stubbornly doctrinaire Russian, although when he stands in profile and juts out his lower lip, he bears a more than passing resemblance to Nikita Khrushchev in a sulk. His rigor has long since been eroded from within, and he yearns to escape from what he views as a lifetime spent in fruitless bargaining.

"You know what I'm dying to hear an American talk about?" he admits in all blue-eyed candor. "Mickey Mouse." It is the American, fresh on the job and as unyielding as a dress shirt, who finds it hard to shed the heavy mantle of destiny. "Stay here long enough," the Russian warns him, "and all we can enjoy is a totally meaningless conversation."

The prospects of accord are remote; hope is a will-o'-the-wisp. But in the play's four scenes -- one for each season -- this pair continues talking, arguing, probing -- and an unlikely friendship is formed. "Our time together," notes the Russian, after the treaty they have been painstakingly negotiating falls apart, "has been a great failure. But a successful one."

That is not just a facile quip. The arms race itself is a supremely irrational endeavor -- the ultimate game in an absurd universe. The dynamics are dismayingly complex, and Washington and Moscow may not even be playing by the same set of rules. Perhaps, Blessing suggests, the illusion of talks is all either side really wants. Or perhaps the problem has mushroomed beyond man's ability to solve it. Failure is all but preordained.

What these negotiators do come to understand, however, is one another. They are as different as borsch and barley, but on a park bench in the pristine woods outside of Geneva, they eventually discover a shared conscience. That may be an ineffectual tool under the circumstances -- rather like using a screwdriver to dismantle a nuclear reactor -- but it's the only tool they've got. If mankind still stands on the brink at the conclusion of "A Walk in the Woods," at least these two odd fellows of diplomacy have taken one step back from the precipice.

Blessing's play is inspired by an incident that occurred during the 1982 disarmament talks in Geneva. Negotiations were seemingly deadlocked, when Paul Nitze, who headed the American mission, and Yuli Kvitsinsky, his Soviet counterpart, broke from the table and took to the woods. There, freed from encumbering committees and the scrutinizing press, they apparently had a meeting of minds. Temporary, as it turned out, but a meeting nonetheless.

"A Walk in the Woods" doesn't purport to tell us what actually transpired back then. Nor does Blessing claim a real-life authenticity for his characters, John Honeyman and Andrey Botvinnik. But the dramatist in him can't help wondering how two men -- seasoned and combative diplomats, entrusted with firm directives from on high -- might get beyond dogma and debate. Might even come to shore one another up in frustration and despair.

"A Walk in the Woods" is another instance of the regional theater nurturing Broadway. The play was first mounted last year at the Yale Repertory Theatre, then enjoyed a production, staged by Des McAnuff, at the La Jolla Playhouse. McAnuff has also directed this version, which was under consideration to play the Kennedy Center, until the center, following the scent of big bucks, opted for the egregious "Mail" instead.

Well, "A Walk in the Woods" probably won't make any money. But it throws out two hours of provocative ideas, eminently worth entertaining. Maybe the most exciting thing in the world, opines the Russian, is knowing that you can destroy the world. Without nuclear arms, he points out, America would be nothing more than "a rich Canada," and the Soviet Union, "an enormous Poland." The implications suggest that Blessing is not overly reassured by the recent INF Treaty.

The dialogue is interwoven with wistful music by Michael S. Roth, and the lovely Chekhovian set, designed by Bill Clarke, delicately reflects the changing seasons. The production's main shortcoming is Waterston, who used to be an appealing actor, but in this, as in the recent "Benefactors," can't seem to avoid coloring his emotions with stridency and righteousness. His character is possessed of a fierce idealism, but idealism in Waterston's performance registers as an insistent whine. Carping is not what "A Walk in the Woods" is all about.

Prosky, however, takes it in stride, twinkles even, while Waterston fulminates. And that twinkle alone gives you reason to hope.

A Walk in the Woods, by Lee Blessing. Directed by Des McAnuff. Set, Bill Clarke; costumes, Ellen V. McCartney; lighting, Richard Riddell; music, Michael S. Roth. With Robert Prosky and Sam Waterston. At the Booth Theatre in New York.