But these modifications did not clarify how great a possibiltiy of persecution must exist before the alien can qualify for withholding of removal.

Under the new Immigration Reform and Control Act, which went into effect on May 6, illegal aliens who arrived prior to Jan. 1, 1982, qualify for legal status.

An illegal alien with income below the official poverty level may still qualify for legal status if he has a history of regular employment.

The Court also decided an important immigration case today with a ruling permitting some 200,000 undocumented aliens to qualify, belatedly, for the amnesty offered by the 1986 immigration law.

As a result, more aliens will qualify, and intense debate over the wisdom of the new rules is likely in Congress.

Under the new rules, an alien may qualify for asylum on the basis of the applicant's own statements, without corroboration, if the testimony is "credible in light of general conditions" in the alien's home country.

But in final rules issued today, the agency said such aliens may qualify if they have since returned to the United States.

Thus, for example, an illegal alien who left the United States for the Christmas holiday last year but returned in January might qualify for legal status under the new rules.

But Verne Jervis, an immigration service spokesman, predicted that most aliens still will not qualify because they cannot show a well-founded fear of persecution.

Illegal aliens who lived in Texas or California, traveled to Mexico and surreptitiously re-entered the United States could qualify for amnesty under the old rules, he said in an interview.