New York, New York - A panel of 12 jurors was sworn in on Thursday to sit in judgment of Donald Trump at the unprecedented criminal trial of a former US president.

"We have our jury," said Judge Juan Merchan after a day of intensive questioning of dozens of potential jurors by prosecutors and Trump's defense attorneys.

Merchan said he hoped to complete the selection of six alternate jurors on Friday and hold opening arguments in the blockbuster case on Monday.

Trump (77), who is seeking to recapture the White House in November, is accused of falsifying business records on the eve of his 2016 election victory to cover up a sexual encounter with a porn star.

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He has pleaded not guilty.

Seven jurors had been selected as of Tuesday, but that number fell to five on Thursday following the release of the two jurors who had already been sworn in. One was excused because she had concerns her identity had been revealed, and the other following doubts about the accuracy of his answers during questioning.

Seven jurors were selected Thursday afternoon, along with one alternate. They looked somber as they raised their right hands and swore to hear the case in a "fair and impartial manner."

Trump, dressed in a dark suit and blue tie, watched silently from the defense table as the jurors took the oath.

To protect the anonymity of the New Yorkers randomly selected for jury service, Merchan asked reporters on Thursday to stop providing physical descriptions of potential jurors and not identify where they work.

A unanimous verdict will be required to convict Trump.

Potential jurors were grilled by prosecutors and defense attorneys about their media consumption, political donations, education, and whether they have ever attended a pro- or anti-Trump rally.

About half of the first batch of 96 jurors ushered into the courtroom on Thursday were immediately excused after saying they could not be fair and impartial in a case involving one of the most famous and controversial men in the country.

The trial, expected to last six to eight weeks, comes as Trump is taking on Democratic President Joe Biden in a bid to make a shock return to the White House.

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Trump has been ordered by the judge to attend every day, forcing the real estate tycoon to exchange the campaign trail for the unglamorous confines of a rundown courthouse.

The judge has made it clear he will not tolerate Trump's habitual grandstanding, warning him earlier this week when he began to mutter toward prospective jurors.

"I will not have any jurors intimidated in this courtroom," Merchan said.

Merchan has also warned Trump against intimidating people connected to the case on social media.

The judge scheduled a hearing next week to consider whether Trump should already be held in contempt for violating a partial gag order prohibiting him from attacking witnesses, jurors, court staff or their families.

If convicted of falsifying business records, the twice-impeached Trump would potentially face prison, but legal observers say fines would be more likely.