US President Donald Trump (C) rails on the Federal Reserve's monetary policy in a speech delivered at the Economic Club of New York in New York, the United States, Nov. 12, 2019. (Xinhua/Wang Ying)

The conservative majority on the Supreme Court appeared sympathetic on Tuesday to US President Donald Trump's decision to end a program which protected nearly 700,000 young immigrants known as "Dreamers" from deportation.

The Deferred Action for Childhood Arrivals (DACA) was created by former president Barack Obama and allows young undocumented immigrants brought to the country illegally as children - nicknamed "Dreamers" - to stay and work in the US.

Trump, who takes a hardline stance on immigration, announced in September 2017 that he would terminate the DACA program, and it expired last year after Congress failed to come up with a replacement.

Challenges to the phaseout of the program, which enjoys bipartisan support, eventually ended up before the nine ­justices on the nation's top court.

A ruling is not expected ­until next year, when the US presidential election campaign - in which immigration is likely to be a hot-button theme - will be at its height. 

Trump weighed in on Tuesday as the court heard arguments, claiming that "many of the people in DACA, no longer very young, are far from 'angels.' Some are very tough, hardened criminals."

DACA applicants are not eligible if they have a criminal record.

Trump also left the door open, however, to an agreement with Democrats in Congress if the Supreme Court - where conservative justices hold a five to four majority - scraps the program. "If Supreme Court remedies with overturn, a deal will be made with Dems for them to stay!" he said.

The conservative justices on the Supreme Court appeared to side on Tuesday with the Trump administration's arguments for ending DACA, while the liberal justices appeared skeptical. Trump-appointed justices Brett Kavanaugh and Neil Gorsuch led an intense grilling of Theodore Olson, an attorney representing the "Dreamers," on whether he believes the administration has the authority to terminate the DACA program.

If the Supreme Court fails to extend legal protection to the "Dreamers," they are not expected to be automatically deported; most will probably slip quietly into the shadowy life of the undocumented, for whom working and studying is fraught with difficulty.

The vast majority of the "Dreamers" are from Mexico, and smaller numbers come from El Salvador, Guatemala, Honduras, Peru, South Korea, Brazil and other countries.