Peking — Alan Pakula's latest project is also his most ambitious and promises to require all his skills - not only in filmmaking but in diplomacy. The veteran American film director recently told a press conference here in the Chinese capital that he had decided to film ''Spring Moon,'' Bette Bao Lord's bestseller, with an all-Chinese cast speaking English and with major scenes shot in the garden city of Suzhou, where much of the action takes place.
Speaking at the same press conference, Mrs. Lord, who was born in China and came to the United States when she was eight, said she hoped to ''merge my two lives (in China and America) in this project.'' She said she wrote her story for Westerners, never dreaming that Chinese might also be interested in it.
''Spring Moon'' is the story of a woman whose life spanned the tumultuous years from the days of the empress dowager at the end of the 19th century to those of Mao Tse-tung and the cultural revolution of 1966.
''It is as challenging and difficult and exciting a role for a woman as any I've been involved with,'' said Mr. Pakula. ''And I say that as a director who has had five or six actresses win Academy Award nominations, of whom two won the Academy Award.'' (Jane Fonda in ''Klute'' and Meryl Streep in ''Sophie's Choice'').
''It's a remarkable role, and it must be played by a Chinese woman. The days of Paul Muni and Luise Rainer getting up and making up three hours every morning to look Chinese are over.''
Pakula is allocating plenty of time to his project, which requires the full cooperation of the Chinese authorities, even though it will not take the form of a joint venture or of a co-production. This is his first visit to China, and he expects to make many more before even getting around to the shooting.
If Pakula gets the cast he wants and the Chinese authorities allow him to shoot major scenes in China, he expects to start filming in 1985 and to release the movie in 1986. It will be a medium-budget film, he said, costing around $15 million.
He is not looking to the Chinese authorities for any financial participation, but for cooperation in permitting Chinese actors and actresses to participate in the film and in shooting major scenes in Suzhou and other Chinese locales.
So far, he said, the Chinese response has been warm, even enthusiastic. He has given them a synopsis of the script, which he is writing himself. According to Mrs. Lord, several Chinese translations of the book are already being prepared.
Pakula noted that several previous co-production or cooperation projects had not worked out, and he felt that in his case it was essential that both sides get to know each other over a period of time and be absolutely sure that they agreed on every detail of the project before anything was signed.
So far, he noted, he has received excellent cooperation: He has visited studios in Peking and Shanghai, has seen film clips to familiarize himself with the kind of talent available and the way in which films are made here, and has been to Suzhou to get a feeling for the place.
He acknowledged that one of his major problems will be getting Chinese actors and actresses to play Chinese roles while speaking English. He intends, after casting has been completed, to have every participant read both the book and the script thoroughly in Chinese so as to get inside the story and the character.
Meanwhile, they would also be taking English lessons. Finally, before shooting starts in 1985, there will be six to eight weeks of rehearsals.
Meryl Streep, Pakula pointed out, spoke no German or Polish before ''Sophie's Choice,'' but ''she is a remarkably gifted woman with a superb ear.''
''I'm not saying the world is full of Meryl Streeps,'' Pakula said, but he has already had personal contact with Ying Ruocheng, who played the title role in Arthur Miller's ''Death of a Salesman'' this year and who is China's leading actor of international stature. He seems confident that with Mr. Ying's help he will find a Spring Moon worthy of winning an Academy Award and of bringing international acclaim to China.