Imprisonment would be an unprecedented step in the historic trial, which stems from a hush money payment made to porn star Stormy Daniels in the final weeks of the 2016 election.

Trump has pleaded not guilty and denies wrongdoing.

But the judge said Trump’s “continued, wilful” violations of the gag order amounted to a “direct attack on the rule of law”.

Merchan imposed the 10th US$1,000 fine on Monday for an April 22 broadcast interview in which the former president said: “That jury was picked so fast – 95 per cent Democrats. The area’s mostly all Democrat.”

Merchan found that other statements flagged by prosecutors that mentioned witnesses Michael Cohen and David Pecker did not violate the gag order.

The order prevents Trump from making statements about jurors, witnesses and families of the judge and prosecutors if meant to interfere with the case. Violations are punishable by fines of up to US$1,000 or prison time of up to 30 days.

Last week Merchan fined Trump US$9,000 for nine social media posts that he ruled had violated the gag order.

Trump complains frequently that the gag order limits his ability to make his case to voters in his comeback White House bid.

“He’s taken away my constitutional right to speak,” Trump told reporters outside the courtroom, before the judge fined him.

Prosecutors on Monday later showed jurors business records that documented payments totalling US$420,000 from Trump to Cohen, his former fixer and personal lawyer.

Those payments were listed as legal fees, but prosecutors say they were actually meant to reimburse Cohen for paying US$130,000 to Daniels to keep quiet about a sexual encounter she says she had with Trump in 2006.

Trump denies ever having had sex with Daniels.

Prosecutors say the US$420,000 paid by Trump was meant to cover the US$130,000 Cohen paid to Daniels, along with US$50,000 in other expenses he had incurred. Trump doubled that total to account for taxes and also included a US$60,000 year-end bonus, they say.

A former controller in Trump’s organisation, Jeffrey McConney, testified that he was not aware of any other instance in which the Trump Organisation reimbursed someone so generously.

McConney said he never spoke to Trump about the payments but was told by the company’s top finance official Allen Weisselberg that they were reimbursements.

Another former Trump employee, Deborah Tarasoff, walked the jury through the 34 invoices, ledger entries and cheques stemming from the payments to Cohen, which were made on a monthly basis after Trump won the election. Each represents one of the 34 counts in the indictment against Trump.

Most of the cheques were signed by Trump personally, and prosecutors highlighted his tall, looping signature in thick ink for the jury.

Prosecutors say the payment to Daniels corrupted the 2016 election by keeping the news from voters, at a time when Trump’s treatment of women was a central issue in his campaign against Democratic candidate Hillary Clinton.

They say the altered business records covered up election-law and tax-law violations that elevate the 34 counts Trump faces from misdemeanours to felonies punishable by up to four years in prison.

If found guilty, Trump could face four years in prison, though defendants typically face fines and probation.

The main players in the case have yet to testify, including Cohen and Daniels, whose real name is Stephanie Clifford.