NEW YORK — The classic law of supply and demand dictates: When a sphinx talks, people listen.

So when the famously private and taciturn Robert De Niro wants to speak at length, ears get cocked for a rare windfall of words.

He's uncharacteristically voluble, of course, because he's promoting his second directorial outing, "The Good Shepherd," a tale about the earliest days of the CIA and a fictionalized agent (played by Matt Damon), which opened yesterday.

But he's also willing to discuss why it's been 13 years between directing efforts, his directing influences, the difference between directing and acting, his recent choice of roles, even — grudgingly — how he relaxes, and why he doesn't like to talk about his personal life.

Still, De Niro is highly distracted during an interview. A huddle with production partner Jane Rosenthal delays an interview that was moved up — then pushed back to its initial time. Several cell phone calls pull him away.

When he excuses himself for a third time, he graciously says: "Sorry I'm preoccupied. And I want to do justice to the interview."

And he does, eventually.

Once he settles down to talk, De Niro says he wanted to do a movie about the CIA for a long time — and, no, playing an ex-spy in comedies with Ben Stiller didn't count.

"I had always been interested in the Cold War and espionage," says the 63-year-old two-time Academy Award winner. "It was just kind of a fascinating part of our history."

Then along came the "The Good Shepherd" script from Eric Roth (whose screenplays include the Oscar-winning "Forrest Gump" and Oscar-nominated "Munich" and "The Insider") although it encompassed an earlier period (1939-61) than De Niro initially wanted to cover.

Aside from the geopolitical relevance that the movie might have now given the debate on treatment of suspects in the war on terrorism, the personal damage is a major focus.

In the movie, Damon's Edward Wilson neglects his wife (Angelina Jolie) and son as he resolutely pursues his espionage career, resulting in a woman whose spirit is broken and a boy overly eager to please his dad.

"I like it when you get the personal side. The personal toll I thought was, to me, interesting, and what I liked about the script when I first read it," De Niro says.

(Asked later, though, why he dislikes talking about his own personal life, he laughs and simply says: "Because it's personal.")

As he researched the film, he traveled to Afghanistan, Moscow and elsewhere, and spent a lot of time with consultant Milt Bearden, who worked in the CIA for 30 years.

De Niro sounds as pleased by Bearden's help with the tiny details, even down to the placement of items in an office, as much as any state secrets or spying stratagems.

"I just didn't want to make any glaring — and whatever he could help us with as far as 'We're doing it this way, is there anything that I should know or be aware of that we could make it more specific?' " De Niro says in his sometimes stream-of-consciousness manner.

Interestingly, while De Niro the actor has been in some of the most harrowing films of the past three decades, De Niro the director kept the violence to a relative minimum in "The Good Shepherd" — though you might see more on the DVD.

"There were a few other little scenes that I shot in the extended version, but I took them out and was always wary of them anyway, and I might put them in the longer version ... I was nervous about — in so many movies, there's people getting shot, this and that, and it seems so gratuitous, and it doesn't have any kind of — it's too easy."

He wanted to make sure the killings were believable and "not too bloody, not too gory."

Those last words might seem like quite a statement coming from a man who cites Martin Scorsese — who directed him in "Mean Streets," "Taxi Driver," "Raging Bull" and "Goodfellas" among others — as a filmmaking influence.

"Well, I've worked with so many directors, and Marty of course eight times. Being in movies as much as I have certainly didn't not help, as an actor," he says. "I'm aware if something's not working."

One huge difference between directing and acting, he says, is the time commitment.

"An actor, you might be shooting for five weeks, and then that's it. Or you're shooting a week here, a week there, it's broken up. As a director, you gotta be there all the time, from the beginning, preproduction, shooting, postproduction. It's a much longer, much more consistent commitment. And that, in itself, is a lot." (De Niro also plays a small role in "The Good Shepherd.")

Not that he's daunted by the task. It's been 13 years since he directed "A Bronx Tale," but the reasons for the hiatus were at least threefold: Projects were long in the gestating period; no other offers came; and he was still acting.

With all that he's juggling — acting, directing again, producing, organizing the Tribeca Film Festival that he founded with Rosenthal to revive lower Manhattan after the Sept. 11 attacks — De Niro concedes that he has problems budgeting his time.

"I don't mind staying busy. Not all the time, but ..." then his voice trails off, as if there's nothing more to say — or that he wants to say.

So then, what does he do to relax?

"Uh, well, going away on vacation. Or at the end of the day, just staying home, reading the paper. Pretty simple stuff."

While he's acted steadily in recent years, some fans and critics feel he's taken roles below his stature in films like "Hide and Seek," "City by the Sea" and "15 Minutes." After all, De Niro is in the pantheon of Hollywood performers of the past four decades, winner of the best-actor Oscar for 1980's "Raging Bull" and supporting-actor for 1974's "The Godfather: Part II," as well as a nominee four other times.

Other critics even cite "Analyze This" and "Analyze That" or "Meet the Parents" and "Meet the Fockers" as mistakes, although many fans appreciated him sending up his own iconic tough-guy roles.

"They're entitled to think that, feel that. I don't know what to say," De Niro says. "Can't always please everybody, and I can't always do the right thing."

He denies ever just going through the motions or going for a paycheck.

"I always try to do my best in whatever I do. It has to be something, whatever I do, that I want to do. Otherwise, there's no point in doing it," he says. "It has to be something that I feel that I can do something with to make it worth my while creatively, besides financially."