Immigration rules to be unveiled Monday will make individual U.S. citizens financially responsible for the immigrants they sponsor - a requirement that may profoundly change who comes to this country and how long they stay.

The rules - part of federal efforts to prevent immigrants from being a “burden” on society - set new minimum income levels for those who may bring in family members. They also transform sponsorship into a contractual obligation: an individual could be sued for failing to support a sponsored immigrant.

Family-sponsored immigrants are by far the largest class of legal immigrants to the United States, making up more than 80 percent of the nationwide total. Based on past data, experts suggest that as many as one-third of families hoping to be sponsors will be unable to meet the new income threshold, which is set at 125 percent of poverty level, or about $20,000 for a family of four.

A San Jose Mercury News review of immigration records underscores the potential.

Half of the 19,783 adult immigrants who came to northern California’s Bay Area in 1995 for “Family Reunification” reported having no occupation.

Nevertheless, those who work with immigrants and sponsoring families suggest the new law will not dissuade many of them - at least at first. New immigrants from countries with family-centered cultures like Vietnam are determined to get their relatives here, they say.

The new immigration rules will take effect Dec. 19.