Washington DC - President Donald Trump arrived at the Supreme Court on Wednesday to attend a politically explosive hearing on his effort to end the birthright citizenship enshrined in the US Constitution.

The White House confirmed late Tuesday that Trump would be attending the hearing.

This is widely believed to be the first time a sitting president has been present for oral arguments at the Supreme Court, let alone in a case brought by his administration, and is likely to be interpreted as heaping pressure on the justices.

The birthright case is at the heart of the 79-year-old's authoritarian attempts to expand his power.

Trump signed an executive order on his return to the White House decreeing that children born to parents in the US illegally or on temporary visas would not automatically become citizens.

Lower courts blocked the move as unconstitutional, ruling that under the Citizenship Clause of the 14th Amendment nearly everyone born on US soil is an American citizen. The Trump administration that the amendment, passed in the wake of the 1861-1865 Civil War, only applies to the children of formerly enslaved people – not migrants or temporary visitors.

The first year of Trump's second term in office has been marked by an alarming slide towards authoritarianism as the Republican expands executive power while sidelining a pliant Congress and routinely attacking the courts.

Just a week ago he launched insults at two of the Supreme Court justices he appointed during his first term because they voted against his tariff policies in another major case. The Republican president also called judges that did not side with him "rogue" and "criminal."