U.S. Immigration and Naturalization Service agents yesterday raided workplaces in nine major cities in the first day of a week-long campaign to oust illegal aliens from "quality" jobs legal residents might like to hold.

The campaign, Project Jobs, is an experiment to see if, during periods of high unemployment, citizens and other legal residents will take work they might otherwise avoid.

After illegal aliens have been arrested, INS agents will notify unions or employment services of vacancies in hopes they will be filled by legal residents. Two or three weeks later, officials said, they will make a random check to see what happened.

"We are trying to do something different," said Joseph Salgado, associate INS commissioner for enforcement. He said 3,000 to 5,000 illegal workers could be apprehended. Many could be deported.

Salgado said the agency is "looking for quality versus quantity" by focusing on better-paying jobs in such areas as computer manufacturing and construction instead of farms and restaurant kitchens, where large numbers of illegal aliens traditionally are employed. "We can't get American strawberry pickers in fields," Salgado said.

Project Jobs will concentrate in Houston, Los Angeles, New York, Newark, Chicago, Detroit, San Francisco, Denver and Dallas. Salgado said these areas have high unemployment, a number of higher-paying jobs held by illegal aliens (according to INS sources) and adequate detention space, Salgado said.

Asked if he thinks legal residents will take the jobs, Salgado replied, "We're going to find that out. It's going to be an interesting experiment." Data from the follow-up survey "may dispel a lot of myths; maybe no Americans want those jobs," Salgado said. Other INS officials said that if the vacant jobs are refilled with illegal workers then it would support sanctions against employers, to discourage the practice.

Arnoldo S. Torres, executive director of the League of United Latin American Citizens, said the program will promote a misconception that illegal aliens are responsible for current high unemployment.