WASHINGTON — The Trump administration is expected to issue a proposal in coming weeks that would make it harder for legal immigrants to become citizens or get green cards if they have ever used a range of popular public welfare programs, including Obamacare, four sources with knowledge of the plan told NBC News.

The move, which would not need Congressional approval, is part of White House senior adviser Stephen Miller’s plan to limit the number of migrants who obtain legal status in the U.S. each year.

Details of the rulemaking proposal are still being finalized, but based on a recent draft seen last week and described to NBC News, immigrants living legally in the U.S. who have ever used or whose household members have ever used Obamacare, children’s health insurance, food stamps and other benefits could be hindered from obtaining legal status in the U.S.

Immigration lawyers and advocates and public health researchers say it would be the biggest change to the legal immigration system in decades and estimate that more than 20 million immigrants could be affected. They say it would fall particularly hard on immigrants working jobs that don’t pay enough to support their families.

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Many are like Louis Charles, a Haitian green-card holder seeking citizenship who, despite working up to 80 hours a week as a nursing assistant, has had to use public programs to support his disabled adult daughter.

Using some public benefits like Social Security Insurance has already hindered immigrants from obtaining legal status in the past, but the programs included in the recent draft plan could mean that immigrant households earning as much as 250 percent of the poverty level could be rejected.

A version of the plan has been sent to the White House Office of Management and Budget, the sources said, the final step before publishing a rule in the federal register.

A spokeswoman for the Department of Homeland Security said, “The administration is committed to enforcing existing immigration law, which is clearly intended to protect the American taxpayer by ensuring that foreign nationals seeking to enter or remain in the U.S are self-sufficient. Any proposed changes would ensure that the government takes the responsibility of being good stewards of taxpayer funds seriously and adjudicates immigration benefit requests in accordance with the law.”

Miller, along with several of his former congressional colleagues who now hold prominent positions in the Trump administration, have long sought to decrease the number of immigrants who obtain legal status in the U.S. each year. And even before the rule is in place, the administration has made it more difficult for immigrants to gain green cards and for green-card holders to gain citizenship.

Image: Immigrants From Over 50 Countries Become U.S. Citizens At The New York Public Library

In fiscal year 2016, the last full fiscal year under the Obama administration, 1.2 million immigrants became lawful permanent residents, or green-card holders, and 753,060 became naturalized U.S. citizens, according to data from U.S. Citizenship and Immigration Services.

Data from the first quarter of fiscal year 2018 indicates that the administration is…