NEW YORK (AP) _ There are millions of longtime legal aliens out there - ''green card'' holders who for years have been eligible for U.S. citizenship, but choose not to be American. Uncle Sam hopes to change their minds.

The Immigration and Naturalization Service recently launched a drive to woo immigrants to citizenship, believing it will help them integrate better in U.S. society and reduce anti-immigrant sentiments harbored by some Americans.

But it could be a hard sell. Resident Alien card holders enjoy all the rights of Americans except they can't vote or run for office. They are subject to the same obligations, too - they pay taxes and can be drafted in wartime.

The ''green card'' gives legal access to high-paying U.S. jobs. But once they get it, many immigrants stop there.

Some would like to become naturalized Americans, but are turned off by the bureaucratic hurdles; there's lots of paperwork, they must speak English and know something about U.S. history.

But others don't want to be American. They remain loyal to their countries or plan on returning home.

What has changed from a century ago, when most immigrants sought to assimilate?

Frenchman Antoine Blanchard, a retired New York accountant and 30-year green card holder, said with local foreign-language publications and TV and radio broadcasts, aliens can ''surround themselves with their own culture.''

''Fifty years ago, every trip was an adventure. People took all the money they had, and didn't have any way of returning. But now, with jet planes, it's no longer the same, you can return home in a day. It retains the link.''

He first came with his American wife in 1962, then stayed after they divorced. He has long been eligible for U.S. citizenship, but feels he's still an outsider here - and doesn't mind. ''I prefer to keep my contact, my roots, the culture in which I was raised.''

In New York, French-speaking African taxi drivers work nights listening to the FM station that broadcasts Radio France Internationale's African news program. Some say they're saving up to return home and open a business.

Ethnic enclaves, such as where Haitians and Hispanics live in Miami and New York, are like large lumps that don't dissolve in the American melting pot. In these places, little or no English is heard in stores, on streets or car radios.

Out of the current 10 million green card holders, 6.5 million have lived long enough in the United States - five years or more - to be eligible for citizenship, the INS says.

Hispanics make up the largest group. The National Association of Latino Elected and Appointed Officials, which promotes naturalization, did a survey in 1988 on why most Hispanic immigrants don't become citizens.

Of 1,636 eligible Hispanics interviewed nationwide, only a third had become U.S. citizens. Of the remainder, roughly half hadn't done so mostly because they saw no benefits. The rest felt the process was too complicated, according to Rosalind Gold, a senior research associate with the Los Angeles-based group.

She praised the latest INS naturalization drive, though she noted that much of the funding for the effort has been held up by Congress.

''The INS for the last few decades has thought of naturalization as a personal choice, that the U.S. should remain with a neutral attitude,'' Gold said. ''For the first time, the INS has tried to make an effort to make the 'N' in the INS have some meaning.''

The drive is an initiative of INS Commissioner Doris Meissner, who took office a year ago. The INS is sending agents to schools, fairs and non-profit agencies to stress the advantages of citizenship and help people unfamiliar with English or official documents fill out naturalization forms.

U.S. citizens can petition to admit overseas relatives as immigrants much quicker than can green card holders. And there are no travel limits - aliens risk losing their cards if they remain abroad for more than a year.

But those advantages don't entice many longtime aliens.

Kouross Esmeli, 26, moved from Iran to Memphis, Tenn., in 1979, at age 11.

''Originally, I didn't want to (become a U.S. citizen) for ideological reasons. There were lots of things about the U.S. government I didn't like,'' said Esmeli, a graduate student at New York's Columbia University.

He's less concerned about that now. Still, all he can't do without citizenship is vote, ''and I don't care about that.''

The INS and immigrant advocacy groups hope to change such attitudes.

On Spanish-language Mega 97.9 FM radio, an ad by the New York Immigration Hotline urges aliens to become American. A youth tells his mother she could influence government by voting.

At first, she's worried her English isn't good enough to take the citizenship exam, but then says, ''Well, I guess this is my home now.''