Mr. Wong was also working for the first time with a screenwriting partner, the crime novelist Lawrence Block, who had written some scenes based on an outline. While shooting, Mr. Wong constantly revised and added new scenes, often at the last minute. He said he was surprised to find that the actors were not only ready for the challenge - his reputation preceded him - but even excited.

"I wish we had endless time and endless money," Mr. Law said. "It's not often you get to be part of something like this - a living story that's still being decided."

There is a pragmatic side to Mr. Wong's seemingly reckless method. Entire subplots are planned, cast and even shot, only to evaporate. But he recycles ideas as often as he abandons them. A stray segment from "Chungking Express" became "Fallen Angels," while "2046" bloomed from a kernel first planted in "Days of Being Wild," his 1991 breakthrough film.

Similarly "My Blueberry Nights" grew out of a planned omnibus called "Three Stories About Food." One chapter became "In the Mood for Love" (2000). Another, the basis for "Blueberry," was filmed as a short with Tony Leung and Maggie Cheung, and has only been screened once, at the 2001 Cannes Film Festival.

That short, called "In the Mood for Love 2001," contained the blueprint for the Kiss. As Mr. Wong expanded the scenario, it turned into a road movie partly because it would cost too much to shoot entirely in New York. So he contrived a romantic predicament to send Ms. Jones' character on a trip. "She needs time to think so she takes the longest road across America, from the Atlantic to the Pacific," he said.

The next step was to map her route and find at least two pit stops. Crew members went on three cross-country location scouting trips, accompanied twice by Mr. Khondji and once by Mr. Wong. Both took copious photos of highways, diners, motels: slices of Americana in the style of Robert Frank and William Eggleston.

Mr. Wong considered post-Katrina New Orleans, but the logistics were daunting. He opted instead for Memphis, where Ms. Jones would encounter Mr. Strathairn and Ms. Weisz's unhappy couple. (Mr. Wong called the Memphis segment a tribute to Tennessee Williams.) He discovered Ely while driving along Highway 50, often called the loneliest road in America, and decided to place Ms. Portman's story line there.

Mr. Wong asks for complete trust from his actors, but he's also willing to customize their roles to suit them. This was especially so with Mr. Law's character, the cafe proprietor, who started out as a quiet type but grew more boisterous when the actor’s charisma and energy became evident. "I kept telling him to get louder," Mr. Wong said.

More than a month into the shoot, despite the breakneck pace and permanent uncertainty, the atmosphere on set was relatively serene. "There's an incredible calmness to him," Mr. Law said of Mr. Wong.

Even so, there are some basic aspects of production in this country that run counter to his prized spontaneity. Permit applications must be filed well in advance. Union regulations stipulate penalties for long days, precluding the marathon sessions that he has been known to hold.

In Hong Kong "we make films like a family business," he said. "Here everything has to be quite specific. I have to explain to the crew that even though I respect the rules, there's certain things I want to keep my way."

As Ms. Jones put it, "He's open to everything, but he knows what he wants."

BETWEEN takes of the Kiss, Mr. Chang, the production designer, was fussing over Ms. Jones. He rearranged her hair, fanning her curls out on the countertop, and reapplied the spot of cream on her lip. Compared with the exertions of "2046," which called for period re-creations, futuristic sets and a heaving wardrobe of traditional and android couture, this was a breeze.

"I really needed a break from period," Mr. Chang said, smiling.

The cafe location had only been minimally altered. There were hand-painted inscriptions on the glass windows and a new sign outside with Cyrillic lettering. Mr. Chang had also installed a pair of columns to break up the tiny space and mounted mirrors to maximize the angles.

That night Mr. Khondji was working out a complex shot that required him to pan, track and shoot the Kiss through a vase, a cake dish and some beer bottles on the countertop.

After a few takes Mr. Wong asked if the shot would work better if Mr. Law, before swooping in for the smooch, extended his hand to touch Ms. Jones's face. Or, as he put it, "Foreplay or no foreplay?" A vote was taken among those present; the former prevailed. Mr. Law incorporated the maneuver into the remaining takes.

Later Mr. Wong jokingly explained: "I had to ask because in America, sometimes they prefer things macho. I wasn't sure if it should be too tender. In Hong Kong I don't have to ask. I know what a guy would do.”

Most nights the mood music was “The Greatest,” the latest album of dreamy downer ballads by Cat Power. For Mr. Wong the on-set soundtrack was mostly for the benefit of the cinematographer. “The best way for the camera to pick up the rhythm is music,” he said.

Mr. Khondji said that he and Mr. Wong had intended to adopt a casually alert, near-documentary style, using a small crew and natural light. But once they got under way, perhaps through force of habit, the shots became more stylized. Still, Mr. Khondji added: "It's not as perfect as his last two movies. There's no time for perfection."

Mr. Wong left for Hong Kong in September with almost all of "Blueberry," his ninth feature, under his belt and - it would not be a Wong Kar-wai film otherwise - questions surrounding the ending. He said he would likely return in the winter to shoot the concluding scenes.

Reached by e-mail recently, he said he was editing with Mr. Chang and would not make any decisions about additional shooting until he had a first cut. The plan had been to balance the completion of “Blueberry” with preproduction on "The Lady From Shanghai," but Ms. Kidman announced last month that she was pulling out of that film. "None of those reports have been confirmed by anyone involved with the project," Mr. Wong wrote. Without Ms. Kidman, though, he added, "There is no reason to do it."

Over tea shortly before he left New York, Mr. Wong said he was exhausted from the grueling shoot. But far from being fazed by the sense of incompletion, he seemed invigorated: the door remained open, no alternatives had been lost, the story was still alive.

And how might "My Blueberry Nights" end? "I think there will be a second kiss," he said. "But I don't know where."