Washington, Feb 25 (IANS): A new federal regulation that took effect throughout the US could make it more difficult for legal immigrants dependent on government assistance to obtain permanent residency permits, known as green cards.

The so-called "public charge" rule, which went into effect on Monday, also applies to applicants for extension of non-immigrant stay in the US or change of non-immigrant status, reports Efe news.

Amid a months-long legal battle, President Donald Trump's administration will start enforcing the regulation, which may transform the current US immigration system into one with a heavier emphasis on criteria such as a migrants' income, age or academic training.

Although court appeals were still pending, the measure was implemented after the US Supreme Court on February 21 lifted an injunction that had been imposed by an Illinois district court.

The high court had earlier lifted injunctions against the policy that had been imposed by courts in the states of New York, California, Washington and Maryland.

The rule will not apply to immigrants who already have green cards nor to those applying for citizenship.

Refugees and people seeking or have been granted political asylum were also among those excluded from the restrictions.

Trump's run to the White House in 2016 was fuelled in part by his vow to build a wall along the US-Mexico border and take other steps to crack down on illegal immigration.

Although the President enjoys strong backing from within his own Republican Party just over eight months prior to the 2020 general election, some former supporters-turned-critics say he has not done enough in that regard.

But many Republicans also want a partial - or even total - crackdown on legal immigration, warning that conservatives will not be able to win national elections in the future due to a steadily increasing number of traditionally Democratic-voting Hispanics in Texas and other states.