US President Donald Trump leaves after delivering remarks on immigration reform, accompanied by Senator Tom Cotton (R-AR) (L) in the Roosevelt Room of the White House in Washington, US, August 2, 2017. [Photo/Agencies]

WASHINGTON - US President Donald Trump backed legislation set to slash legal immigration on Wednesday by unveiling a "merit-based" system unfavorable for low-skill immigrants.

Introducing what he called the most significant overhaul of immigration in half a century, Trump said the current system "has not been fair" to US workers as it allows entries of low-skill immigrants hired at a lower salary.

Struggling American families "deserve an immigration system that puts their needs first and that puts America first," Trump said in a speech at the White House, joined by the bill's sponsors, Republican Senator Tom Cotton of Arkansas and David Perdue of Georgia.

The Cotton-Perdue bill, or the Reforming American Immigration for Strong Employment (RAISE) Act, was first introduced in February.

The early version of the bill was designed to cut legal immigrants onto the United States by 50 percent over the next 10 years.

After being reintroduced with some changes, the bill proposed to eliminate certain pathways to family-based immigration, stipulating that only spouses and minor children of the US citizen and permanent residents would be eligible for green cards.

Meanwhile, the act creates a merit-based system that grades possible immigrants for earning a green card, a major attempt to completely overhaul the family-based approach.

Factors that would be taken into account in the competitive process include English language skills, education, financial capability, and age.

The legislation, Trump stressed, also "prevents new immigrants from collecting welfare and protects US workers from being displaced."

"And that's a very big thing. They're not going to come in and just immediately go and collect welfare," he continued.

The initial bill, stalled in the Senate for several months, was praised by the country's anti-immigration groups, while it is predicted to face an uphill battle through the Congress.

Shortly after the bill was unveiled, Republican Senator Lindsey Graham of South Carolina said the bill would be "devastating" to the US economy "which relies on this immigrant workforce."

Other critics argued that such measures would dissuade skilled immigrants who would otherwise want to come to the United States.