President Donald Trump’s administration will reportedly announce plans that would make it more difficult for legal immigrants to become citizens or get green cards if they’ve used public welfare services, sources tell NBC News.

The plan is apparently the brainchild of White House senior adviser Stephen Miller.

As part of the plan, immigrants who use the welfare programs such as children’s health insurance, food stamps and even Obamacare would be prevented from becoming a citizen or obtaining any legal status in the U.S., according to NBC News.

“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,” a Department of Homeland Security spokeswoman told NBC News.

More than 20 million immigrants could be impacted by the proposed plan, which would need to be approved by Congress, according to immigration advocates. They tell NBC News that it would be the biggest change to the country’s legal immigration system in decades.

Miller and other Trump administration have expressed a desire to decrease the number of legal immigrants wanting official legal status.

About 1.2 million immigrants became permanent residents or received green cards in fiscal year 2016, the last full fiscal year under President Barack Obama, according to data obtained by NBC by the U.S. Citizenship and Immigration services; 753,060 became naturalized citizens.

A 20 percent decline in immigrants would receive green cards and a 10 percent decrease for naturalized citizenship for fiscal year 2018 is expected under the Trump administration, NBC News reports.

Click here to read more of NBC’s extensive report.